WO1999064656A1

WO1999064656A1 - Fibrous batts bonded with thermosetting fiber-binders of certain polyester resins

Info

Publication number: WO1999064656A1
Application number: PCT/US1998/022818
Authority: WO
Inventors: George S. Buck
Original assignee: Buck George S
Priority date: 1998-06-10
Filing date: 1998-10-28
Publication date: 1999-12-16
Also published as: AU1282799A

Abstract

This invention relates to non-woven fibrous batts and pads bonded with certain polyester resin fiber-binders and to processes for their production.

Description

FIBROUS BATTS BONDED WITH

THERMOSETTING FIBER-BINDERS OF

CERTAIN POLYESTER RESINS

Field of the Invention

Background of the Invention

Some years ago processes were developed for producing a fibrous batt by contacting fibers with a dry fiber-binder based on certain thermoplastic polymers. Such processes are described in the following US Patents among others:

Buck et al US 3,993,518, "Buck'518"; and Buck et al US 3,997,942, "Buck '942"; and

Buck et al US 4,047,99 1, "Buck '991"; and

Buck et al US 4,050,997, "Buck'997"; and

Buck et al US 4,051,294, "Buck '294"; and

Buck et al US 4,053,673, "Buck'673"; and Buck et al US 4,053,674, "Buck'674" and

Buck US 4,211,817, "Buck '817"; and

Buck et al US 4,363,680, "Buck'680"; and

Buck US 4,550,050, "Buck'050"; and

Buck US 4,457,793, "Buck'793"; and Buck et al US 4,473,428, "Buck'428"; and

Buck US 4,850,854, "Buck '854"; and

Elsen US 4,869,950, "Elsen".

These prior processes have proven very useful for a number of reasons. First, the noted processes can utilize inexpensive recycled fibers. Such fibers are recovered from garment clippings, textile mill waste, and other waste fibrous products. These materials are sometimes referred to as "shoddy." Second, the patented processes are anhydrous, that is, completely dry, employing neither water nor solvent. Third, the fiber-binder employed is in its solid powdered form. Batts produced by these prior processes find a wide variety of uses. They are useful as pads in mattresses, furniture, chairs and automobile seats. They are also useful as carpet underlay. In fact, these batts can be employed anywhere it is desired to provide resilience, thermal insulation, sound insulation and/or cushioning. These batts can be covered with other fabric or they may be visible to the naked eye. Moreover, these batts can be used almost everywhere that rubber or polyurethane foam have been used in the past. Such batts are, however, superior to foam for many reasons, particularly because they have a greater life under use. Because of their great utility these prior batts have achieved great commercial success. They are currently produced all over the world in quantities greater than about 25 million kilograms, about 25,000 tons, per year. One disadvantage is the relatively high melting point of the thermoplastic resins used as fiber-binders. For example, a batt bonded with a dibutyl -maleate copolymer must be heated to about 195°C (383°F). Such a high melting point is expensive to maintain because of energy costs. Such a high melting point increases the possibility of adverse heat effects on components of the batt. The higher the melting point of the thermoplastic resin in the fiber-binder, the greater the danger that it or other components of the batt will catch fire.

Unfortunately these prior batts and processes for their production suffer from a number of other disadvantages. Batts bonded with fiber-binders of chlorine-containing thermoplastic resins suffer from a number of disadvantages. These chlorine-containing resins employ polymers which include vinyl chloride and/or vinylidene chloride. In these batts, a danger exists that an undesirable release of hydrochloric acid will occur. This hydrochloric acid causes a number of problems in both processes for producing the batts and in methods of using the resultant batts because hydrochloric add, which is toxic and highly corrosive, must be contained in the process apparatus. Such apparatus must be constructed with an airtight enclosure and with a fan to keep the enclosure under a negative air pressure. If the apparatus is opened for inspection, adjustment or repair, workers may be exposed to the toxic HC1 vapors. The vapors escaping from the unit must be contained. Repair costs are increased because of the hydrochloric acid. Provision must be made to safeguard workers. The hydrochloric acid must be neutralized, usually with caustic (NaOH) or lime (CaO), producing as neutralization products respectively impure salt (NaCl), and impure calcium chloride (CaCl ). These neutralization products must be disposed of in a manner consistent with a proper regard for the environment. Such disposal is expensive, but vital. Some environmentalists have suggested that a relationship exists between chlorine and the presence in the environment of dioxin.

While the chlorine in these chlorine-containing batts tends to make the resultant batts somewhat fire resistant, chlorine alone is frequently insufficient. It has become common practice to improve the fire resistance of the batts, by the addition of antimony oxide, boric acid, diammonium phosphate and/or aluminum trihydrate. Unfortunately, such added materials tend to increase the propensity of the chlorine-containing fiber- binder to decompose with a resultant undesirable release of hydrochloric acid. This hydrochloric acid must be captured and scrubbed from the effluent stacks to prevent undesirable air pollution. The amount of hydrochloric acid released during curing of the batt increases sharply at temperatures above 205°C (400°F). The effluent by-products produced during batt curing may produce effluent opacities above acceptable limits. Expensive emission control devices are required for monitoring and control. After formation of these prior batts with white fibers and chlorine containing resins, yellowing of the fibers may occur. Where the fibers are visible, consumer demand is diminished.

The prior batts produced with chlorine-containing fiber-binders, when used in upholstered seats with steel springs, are believed to catalyze rusting of the springs. This can result in undesirable squeaking of the springs.

Batts bonded with chlorine-containing resins have been rejected for use as padding for seats and panels in automobiles. Automobile manufacturers fear that any hydrochloric acid release would damage the printed circuits that are part of the computer and electronic components of modern autos. Many of the prior batts bonded with thermoplastic resins give off a gummy vapor when heated. This gummy vapor appears to come from plasticizers which have been mixed with the resin. Examples of plasticizers are dioctyl phthalate and epoxidized soy bean oil. During the heating process these plasticizers are released. The plasticizers can condense as oily residue on top of the neutralization solution, making disposal expensive. They can also condense as a gummy residue which may ignite in oven exhaust causing fires. Removing this residue is time consuming and expensive. One automobile manufacturer has promulgated an empirical test to measure the suitability of batts for use as padding under the carpet of automobiles. In this empirical test, a sample of the batt is exposed to a temperature of 232°C (450°F) for a period of one hour to simulate heating through the automobile floor by the catalytic converter. After the heating period, the pad is examined to determine whether (1) it has produced any odor, (2) it has discolored and (3) it has lost its shape. The prior batts bonded with chlorine-containing fiber-binders fail this test.

As described in the prior art, these prior thermoplastic binders must be utilized in the form of small particles. One method is to polymerize monomers producing directly a resin of the desired particle size. The high cost of this method makes it commercially impractical. A less expensive method is to form the resin without regard to particle size and then grind it to the desired size. Unfortunately, some of these prior thermoplastic binders are relatively soft and require very long grinding times to achieve the desired particle size. Because of their softness the particles tend to deform rather than fracture. Grinding at cryogenic temperatures is of limited success, but is expensive. In recent years the cost of all the noted prior thermoplastic fiber-binders has increased dramatically. This increase has resulted in increased costs for products employing such prior batts, leading to the substitution of other, inferior, less expensive products.

A great deal of effort has been expended in attempting to reformulate these resins economically to lower their melting points. Unfortunately, these attempts have met with only very limited success. In one attempt, a copolymer of vinylidene chloride and vinyl chloride was converted to a terpolymer by introducing other vinyl monomers, such as vinyl acetate and dibutyl-maleate. It was believed that the resultant terpolymer would have a melting point lower than that of the copolymer. In another attempt, mixtures or alloys of two or more thermoplastic resins were employed. An attempt to use polyolefms was unsuccessful because of difficulty in grinding and the propensity of the polyolefms to produce, during grinding, fibers rather than small particles. More recently some success has been achieved when the prior thermoplastic fiber-binder is contacted with the fibers of the batt by blowing it through a fully formed batt. However the thickness of such a batt is limited to about 5 cm (2 inches) because of the tendency of the thermoplastic fiber-binder to fail to penetrate the batt fully. Increasing the air speed through the batt has been only partially successful. As a result, such process is limited to those employing preformed batts of less than 7 cm (3 inches).

These prior batts can be cold molded but cannot be hot molded. In the cold molding process, the batt is heated and placed in a cold mold until the batt cools to the temperature of the mold. In the hot molding process, the batt is placed in a hot mold. After a certain time, the batt is removed from the hot mold. A demand exists for batts which can either be hot molded or cold molded.

A completely unrelated, non-analogous field of electrostatic coating also has a number of problems related to the disposal of waste coating powders. In this field, the substrate to be coated, which may be an automobile body, is given an electrical potential different from a powder spray gun. Coating powder is projected through said gun in a gas stream toward the substrate. Some of the coating powder does not adhere to the substrate and is collected as scrap. A portion of the powder, which is entrained in the air, is then recovered in filters as scrap. Much of this scrap cannot be reused without adversely affecting the resultant coatings. The scrap must be disposed of in an environmentally responsible manner. The disposal of this scrap is a burden on the coating factory. Some factories burn the scrap, whereas others pay to have it transported to an acceptable land fill. Today, millions of pounds of scrap material are injected into the environment annually. If the scrap is burned a danger exists of contributing to air pollution. If the scrap is placed in a land fill a danger exists of contaminating drinking water sources.

Other "off-grade" or scrap material is available from the manufacturer of the coating powder because of defects, poor color and/or the presence of contaminants that make the material unsuitable for use in the powder coating industry. Such material poses a similar disposal problem. Objects of the Invention

Accordingly it is an object of the present invention to provide fibrous batts substantially free from one or more of the disadvantages of batts and pads made by prior processes. Another object of the present invention is to provide an improved fibrous batt substantially free from one or more of the problems of prior batts.

Still another object is to provide batts and pads utilizing a fiber-binder which is free from chlorine.

Yet another object is to provide improved batts and pads which do not contain or release hydrochloric acid.

Still another object is to provide improved batts and pads which are bonded with a recycled, readily available materials.

An additional object is to provide improved, adequately bonded batts and pads in thickness greater than about 5 cm (2 inches) by contact with a fiber-binder. Still another object is to provide improved pads wherein the bending resistance of the batt or pad can be achieved by simply controlling the time and temperature at which the batt is cured.

Yet another object is to provide improved batts and pads wherein the particles of fiber-binder have a greater affinity for the fibers than heretofore. An additional object is to provide improved batts and pads manufactured at lower temperatures than previously possible, with a resultant energy savings.

Still another object is to provide improved batts and pads equivalent in properties to prior batts, but employing less fiber-binder.

An additional object is to provide improved bonded fibrous batts and pads which utilize a fiber-binder that can readily and inexpensively be ground to the desired particle size.

Yet another object is to provide improved batts and pads from binders which do not deposit a gummy residue during the heating step required during batt formation

Still another object is to provide a batt or pad which can be both cold molded and hot molded. In this connection, it is particularly important that the batt does not require a toxic resin like phenol formaldehyde. Another object is to provide an improved batt or pad which meets the tests for usefulness as an automobile carpet pad.

A further object is to provide a hot moldable batt without requiring the use of phenolic resins which produce toxic fumes, undesirable odor, and unacceptable odor from the curing ovens.

The above and other objects are accomplished by providing improved bonded fibrous batts and pads in the manner described in the following description and drawings.

Brief Description of the Drawings

Figure 1 is an elevational view of an apparatus suitable for manufacturing the batts and pads of the present invention.

Figure 2 is a plan view of the apparatus of Figure 1. Figure 3 is a sectional view taken along line 3-3 of Figure 2. Figure 4 shows a portion of another apparatus suitable for manufacturing the batts and pads of the present invention. Figure 5 is a schematic representation on a greatly enlarged scale showing the raw batt of the present invention with the particles of fiber-binder adhering to the batt prior to curing.

Figure 6 is a view similar to that of Figure 5 but showing the cured batt with the fibers bonded at their intersections with the fiber-binder of the present invention. Figure 7 is a schematic representation of a hot molding process employing a batt of the present invention at that stage of the process when the mold is open.

Figure 8 is a schematic representation of a hot molding process employing a batt of the present invention at that stage of the process when the mold is closed.

Figure 9 is a molded batt or pad produced by the process of Figures 7 and 8. Figure 10 is a graph showing the unexpectedly greater bending resistance of pads of the present invention compared with those of the prior art when bending resistance is measured in the transverse direction.

Figure 11 is a graph showing the unexpectedly greater bending resistance of pads of the present invention compared with those of the prior art when bending resistance is measured in the running or machine direction. Figure 12 is a side view of an apparatus used for measuring batt or pad bending resistance as that term is used herein.

Figure 13 is a view of the apparatus of Figure 12 taken along line 13-13 of Figure 12 before measuring. Figure 14 is a view of the apparatus of Figure 12 taken along line 13-13 of Figure

12 during measuring.

Summary of the Invention

According to the present invention, there is provided a non-woven batt comprising fibers bonded with a fiber-binder, the binder comprising: (i) a solid polyester resin having polyester groups, and

(ii) a coreactive effective amount of a cross-linking agent reacted with terminal groups of the polyester resin; wherein the batt produces no formaldehyde or hydrochloric acid at an oven temperature of 232°C, and wherein the batt has a humidity resistance of over 100 hours measured by test

463PB-9-01, and wherein the fibers do not melt or decompose at temperatures below 100°C, and wherein the fiber-binder has a glass plate flow length of from about 15mm to about 150mm before being bonded to the fibers, and wherein the fiber-binder has an average particle size from about 1 to about 200 microns.

According to the present invention, the improved bonded, non-woven, batts and pads of fibers result from the following steps;

I. providing a dry, solid, particulate, latent-curable, thermosetting, fiber-binder which is an intimate mixture of

A. a solid polyester resin having: (a) polyester groups; (b) a molecular weight above about 2000; (c) a glass transition temperature above about 40°C; (d) a melting point above about 70°C; and

B. a coreactive effective amount of a cross-linking agent which reacts with the terminal groups of the polyester resin; and then II. contacting fiber-binding amounts of the fiber-binder with the fibers to form a raw batt with the fiber-binder loosely adhering to the fibers of the batt; and then

III. heating the raw batt to a cross-linking temperature above the melting point of the fiber-binder but below the scorching or melting point of the fibers thereby melting the fiber-binder whereupon the fiber-binder flows to intersections of the fibers and subsequently at least partially reacts with the cross-linking agent with the terminal polyester groups of the polyester resin thereby converting the raw batt into a hot cured batt; and then

IV. cooling the hot cured batt. Throughout this application, the hot cured batt is frequently referred to as a cross- linked batt or semi-cross linked batt to further distinguish the mechanism of the inventive process from the prior art. However, it should be understood that the batt itself is only physically cross-linked with the melted particles of resin which have themselves been cross-linked or partially cross-linked by the chemical reactions described herein. According to another aspect of the present invention the time and temperature of the heating step, Step III, can be limited such that the cross-linking agent reacts with fewer than all the polyester end groups and preferably from about 5 to about 40 percent of the end groups of the polyester resin thereby converting the raw batt into a hot, semi- cross-linked batt which is subsequently cooled. This semi-cross-linked batt is then placed between open male and female molds. The molds are closed, causing the semi- cured batt to take the form of these molds. The male mold, the female mold, and the semi-cured batt are heated to a crosslinking temperature above the melting point of the fiber-binder but below the scorching or melting point of the fibers thereby softening the fiber-binder and reacting the cross-linking agent with the remaining end groups of the polyester resin. This converts the semi-cured batt into a fully cured batt in the form of shaped article.

Detailed Description of the Invention

The polyester resins of the present invention, most broadly stated, are a product which results from the esterification reaction of a polycarboxylic acid and a polyol. However, in practice the constituents of these resins are almost always a dicarboxylic acid and a diol oil. Most commonly terephthalic acid or isophthalic acid are reacted with glycols such as ethylene glycol, propylene glycol, di-ethylene glycol, 1 ,4 butane diol, 1 ,6 hexane diol, neo-pentane diol etc. Because of cost and other considerations, terephthalic acid and ethylene glycol are the most commonly used acids and glycols and will be used herein, without limitation to other options, to illustrate the polyester resins useful in making the improved batts and pads which are the subject of the present invention.

Polyester resins of the types described above are most commonly used as thermoplastics to make such products as fibers and films, including films to make beverage bottles. Generally the molecular weight of these resins ranges from 40,000 to 50,000, and the typical melting range of polyethylene terephthalate is around 490°F, (254°C). This melting range is too high to make these resins useful as fiber binders. Lower melting point polyesters can be made by utilizing various proportions of isophthalic acid, and diols such as 1,4 butane diol or 1,6 hexane diol, neopentyl glycol, etc. However, these polyesters are considerably more expensive and depending on the molecular weight are very difficult to pulverize to fine powders even under cryogenic conditions.

The methods of preparation of polyester resins are well known in the literature and will not be recited herein. However, it is appropriate and pertinent to this invention to note that polyethylene terephthalate used for making bottles, film, fibers and the like can be recycled to polyesters useful in the present invention by "cracking" them back to lower molecular weight products by "cooking" them in a glycol or a dicarboxylic add. Molecular weights in the range of 2,000 to 10,000 can be achieved in this manner and these may be either predominantly acid-terminated or hydroxyl terminated, depending on the method used. Thus post-industrial and post-consumer polyester scrap can be recycled into the polyester resins used in the present invention. In general, the polyester resins useful in the present invention have either the formula illustrated in la. or lb. shown below. Structures as shown

O O

I I o o I I I I

HOC- W // -C-OCH₂CH₂0-C r.-- / \ COH

la

where n is about 9 to about 45.

It should be noted that the polyester resin will seldom be all la or lb, the ratio depending on the method of preparation. The presence of a hydroxy terminal group acts as a chain length stopper in high acid number polyesters and similarly the carboxy n groups act as chain stoppers in low acid number polyesters. These unbalanced terminals also act to stop the cross-linking reactions described below which are the subject of this invention. As noted above, other glycols and di-ols than ethylene glycol may be used, and part or all isophthalic acid may also be employed without affecting the principle of this invention or its function. However, because of cost and quality considerations the preferred polyester resins are based on the reaction between terephthalic acid and ethylene glycol. An excess of the acid above the stoichiometric ratios yields acid terminated resin, and similarly an excess of glycol or a diol yields hydroxy terminated polyester. These are frequently referred to, respectively, as polyester with a high acid number or polyester with a low acid number. The acid number can be determined by titration. Where the polyester is an acid terminated resin, the acid number ranges from about 25 to about 300, preferably about 25 to about 100, most preferably from about 30- 90. Where the polyester is an hydroxy terminated polyester, the hydroxy number ranges from about 20 to 300, more preferably about 25 to 200, most preferably about 25 to about 100.

The polyester resins useful in the present invention generally have a number average molecular weight of from about 1,000 to about 12,500 and preferably from about 1,500 to about 6,500. In a preferred embodiment, the number average molecular weight is above about 2000.

The polyester resin generally has a glass transition temperature, frequently called "Tg", above about 40°C, and preferably above about 50°C, and a melting point above about 70°C and preferably from about 80°C to about 150°C. The polyester resin can have a widely varying molecular weight as long as it is solid. As is well-known in the resin art polymers are a mixture of individual molecules each having a different distinct molecular weight. The average molecular weight of the preferred polyester resins is between about 1,000 and about 10,000 and is preferably between about 3 ,000 and 13 ,000.

As noted, both hydroxyl functional and acid functional polyester resins are useful in the practice of this invention. Suitable hydroxyl functional resins are described in US Patents 4,124,570, 4,264,751 and 4,275,189, the teachings of which are herein incorporated. Suitable acid functional resins can be prepared using either a one stage process, wherein an excess of acid functional monomers are initially charged to the reactor as disclosed in US 4,740,580 or a two stage process such as disclosed in US 4,085,159 and 4,147,737, the teaching of which are herein incorporated. The polyester resins useful in the practice of this invention can have functionality of from about 2 to as high as 8 or 10, preferably between 2-6 and most preferably between 2.4-4. Semi crystalline resins can also be used as all or part of the polyester resin forming the fiber binder of this invention. As with their amorphous counterparts, they can be primarily hydroxyl terminated or primarily acid terminated with the functionality described above. Semi crystalline resins are characterized by showing a crystalline melting point, Tm, as measured by a differential scanning calorimeter (DSC). Suitable crystalline polyester resins are described in US 4,442,270, US 4,859,760 and US 4,352,924.

The polyester resins useful in the fiber-binders of the present invention may be obtained from scrap powder paint which is available from, for example, paint manufacturers and ultimate users of powder paints. Synonyms of scrap powder paints include fines, oversized materials, distressed materials, obsolete materials, off-grade materials and off-spec materials, by which is meant materials which do not meet independent specifications and/or are out-dated.

The cross-linking agents useful with the selected polyester resin are well-known. They may be prepared according to published procedures or obtained from commercial sources. Examples include beta-hydroxyalkylamides such as Primid, oxazolines, resins comprised of residues of glycidyl methacrylate (GMA), and/or glycidyl acrylate, TGIC, epoxy and novalac resins, blocked polyisocyanates and uretidone resins, polyester resins, TMGU (tetramethoxymethylglycouril) and tetraalkyltitanates.

The fiber-binder can be formulated by a wide variety of well-known methods, one method is simply to mix the finely divided polyester resin and the finely divided cross- linking agent and any other ingredients. All ingredients are then briefly heated until they melt. The ingredients are then rapidly cooled before any substantial cross-linking reaction takes place between the polyester resin and the cross-linking agent. The exact degree to which cross-linking has taken place is difficult to determine but it is estimated that fewer than ten percent of the terminal groups are reacted with the cross-linking agent when the mixture is melted and mixed in an extruder, where the residence time is less than about 60 seconds. The cooled ingredients, which are frequently in the form of a solid sheet, are broken into small chips and then comminuted to the desired particle size.

As is well-known in the art, as soon as a polyester resin is mixed with the cross- linking agent, the crosslinking reaction begins slowly to take place. Lower temperatures inhibit the reaction, whereas higher temperatures favor it. As the reaction progresses, those skilled in the art have identified three distinct stages, namely, the "A-stage", where the mixture is soluble in organic solvents, and is fusible, by which is meant it melts and flows; the "B-stage," wherein the mixture is fusible but insoluble; and the "C-stage", wherein the mixture is both insoluble and infusible. The fiber-binders of the present invention go through these same stages. When first contacted with the fibers the fiber-binder is in the A-stage. When partially cross- linked the fiber-binder is in the B-stage. Batts having the fiber-binder in this stage can be hot or cold molded. When fully cross-linked the fiber-binder is in the C-stage. The polyester resin and the cross-linking agent may be mixed in. The particles of the fiber-binder have an average size from about one to about 200 microns, preferably from about 5 to 50 microns. When the particles have a size smaller than 10 microns they can advantageously be mixed with particles having a larger size. If the average particle size is greater than about 40 microns there may be a reduced efficiency in the production of firm resilient batts. The fiber-binder can be applied to the fibers in widely varying ratios but the fiber- binder generally comprises from 2 to 40 and preferably from 5 to 30 weight percent based on the combined weight of the fibers and the fiber-binder. The fiber-binders of the present invention are solid; they are neither aqueous solutions, nor solutions employing other solvents. They are free from solvents and water. Glass plate flow length is a significant characteristic of fiber-binders useful in the present invention. Glass plate flow length is determined by pressing the fiber-binder into a mold to form a pill or cylinder 12 mm in diameter and 6 mm high. This cylinder is is placed on a hot plate at a temperature of 190°C (375°F) at an angle of 35° to the horizontal. The length of the streak made by the cylinder, in one minute is termed the "hot plate flow". A fiber-binder in the C-stage that does not flow at all will have a glass plate flow of 12 mm, i.e., the diameter of the cylinder. Fiber-binders in the early A-stage can have glass plate flows that exceed 160 mm. Glass plate flow provides a simple and convenient method to determine the degree of cross-linking between the polyester resins and the cross-linking agent. The described test also demonstrates one fiber-binder characteristic making the fiber-binder optimally useful in this invention. The fiber- binders of the present invention generally have glass plate flow lengths of from about 15 to about 150 mm and preferably from about 35 to about 125 mm. Others skilled in the art sometimes refer to "hot plate flow" as "glass plate melt flow" or "melt flow".

Fillers and colorants may be added to resins. Fillers are usually less expensive than resins. This permits a filled resin to be made at a cost lower than a fiber-binder which is free from filler. Although fillers are not required to be present in the fiber- binders of the present invention, when present, they provide new and unexpected results. It is possible to use filled fiber-binders and achieve the same batt properties as with unfilled fiber-binders. While this effect is not fully understood, it is believed that after the comminution of the filled resin, particles of filler protrude from the surface of the fiber- binder particle. However, upon such particles being heated, a new and novel structure is produced. Apparently the mixture of polyester resin and cross-linking agent melt and flow, completely surrounding the filler particle. This structure may be thought of as a concentric sphere with the melted, sticky, fiber-binder, then in the A-stage or early B- stage, forming a covering on the outside. This covering is completely adequate to bond with fibers. The particles of the filler have an average size from about one to about 200 microns, preferably from about 5 to 15 microns. Smaller particle sizes are functional in the present invention, but may cause environmental problems because they tend to be respirable.

In general the fillers are inorganic and insoluble in water. Salts of strong acids and weak bases are suitable, as well as salts of weak acids and weak bases. Silica, aluminum-silicates and alumina are all suitable classes. Examples of preferred fillers include, among others, calcium carbonate, barium sulfate, iron oxides, carbon black, and titanium dioxide.

The fiber-binder can include a wide variety of other additives. Examples of additives include among others: catalysts, dyes, pigments, flow control agents, fire retardants, self extinguishing agents, desiccants and all manner of additives which are used herein for their known purposes. Any catalyst known to accelerate or retard the rate of reaction of the hydroxy or carboxy groups and the active group of the cross-linking agent can be employed. Examples of such catalysts include among others: tertiary amines, imidaxoles amic acids and quaternary ammonium and onium compounds, phosphonium compounds, phenolic compounds, organic and inorganic acids.

Examples of fire retardants include: boric acid, monoammonium phosphate, diamonium phosphate and aluminum trihydrate. These additives can be in the form of liquids or particles so long as the fiber-binder remains solid, has the desired particle size and suffers no adverse affects. The fibers can be contacted with the fiber-binder in a wide variety of ways. The fibers can be loose, in the form of a thin web, or in the form of a batt. The fiber-binder can be sprinkled on the fibers under the influence of gravity or can be entrained in a stream of gas or vapor, advantageously air. Any method which leaves the desired quantity of fiber-binder desirably distributed throughout the batt is acceptable. A wide variety of fibers are useful in the present invention including both natural and synthetic fibers. Natural fibers include cotton, wool, jute, and hemp. Synthetic fibers include those of polyester, nylon, acrylic, rayon, glass and polypropylene. In fact, any fibers or mixture of fibers are acceptable, including those in which the fibers may be new and unused, known as virgin fibers, or those that are waste, reclaimed from garment cuttings, fiber manufacture or textile processing and which do not melt or decompose at temperature below 100°C (212°F). The preferred fibers are those having a denier of 1 to 22 although finer and coarser fibers are also sometimes useful. The heating of raw batt containing the fibers and the uncured fiber-binder can be accomplished by any convenient means such as infrared, or microwave but is most conveniently accomplished by hot air which is passed through the batt. This hot air is heated to a temperature above the melting point of the fiber-binder but below that temperature at which the fibers are adversely affected. Adverse effects include scorching or burning of cellulosic or wool fibers or melting or shrinking of synthetic resin fibers. The heating is generally done at a temperature of from about 100°C (212°F) to about 240°C (465°F) for a time sufficient to permit the fiber-binder to flow to the intersections of the fibers and to cross-link there. This is generally accomplished in from about twenty seconds to about ten minutes, and usually from one to five minutes. Such heating converts the raw batt into a hot cured batt.

After completion of the heating step, the hot cured batt is cooled, preferably to room temperature, by any of a wide variety of means. The batt can be passed through chilled rolls, air can be passed through the batt, the batt can be placed in a cooling chamber or some other means can be used for cooling the batt.

Detailed Description of the Drawings

With reference to the drawings and in particular to Figure 1, an apparatus 10 useful for practicing the process of the present invention is shown. The apparatus 10 comprises an opener or garnet 11, a fiber-binder dispenser 12, a cross laying mechanism 13 and, as shown in Figure 2, an oven 14. The garnet 11 comprises an inlet chute 18 adapted to feed bulk fibers to the rotating drum 19 of the garnet 11. The garnet 11 is also provided with a plurality of tooth rolls 21, 22, 23, 24, 25 which together with the teeth (not shown) on the drum 19, take bulk fibers 20 and convert them to a web 31 which adheres to the drum 19. The web 31 adhering to the drum 19 is transferred to the drum 28 where it is removed by comb 29. The web 31 that is now only between one and 100 fibers thick and is barely self supporting, enters the fiber-binder dispenser 12. While in the fiber-binder dispenser 12, the web 31 is contacted with particles 33, 34 of fiber- binder. The structure and function of the dispenser 12 is described in detail in Buck '680 and in Buck '428. A wide variety of other methods can be employed to contact the fiber-binder with the fibers - Another method performs the contacting of the fibers with the fiber-binder after the fibers have been opened and loosened from a compressed bale and at the stage when they are entrained in an air stream and prior to being deposited on a screen or in the slot of an air lay system for producing non-woven batts. Such air-lay systems of this type are well-known in the trade under the names Schirp, Rando Web, DOA, and others. Still another suitable method for contacting the fibers with the fiber-binder is described in Fleissner U.S. Patent 3,765,971.

Instead of contacting the fibers with the fiber-binder while the fibers are in the form of a web as described above with references to the figures, the non-woven batt can be converted into its final form and the particulate fiber-binder blown through the entire batt. It has been unexpectedly found that the fiber-binders of the present invention penetrate these batts better than do the prior fiber-binders. Furthermore a greater percentage of the fiber-binder is retained in the batt 25 than when prior fiber-binders are used. All such contacting methods are useful in the present invention so long as the contacting is effective. With respect to Figures 1 and 2, the web 39 then goes to the conveyor 41 and thence to the conveyor 42. The lower end of the conveyor 42 is attached to a traveller 43 which moves back and forth on the track 44.

The conveyor 42 is positioned above and at right angles to the other conveyor 45. The apparatus 10 is adjusted such that the speed of the conveyor 42 is several times faster than the speed of the conveyor 45. By virtue of this speed difference, the web 39 is cross laid back and forth on the conveyor 45 thus forming a raw batt 47. In one embodiment of the invention, the raw batt 47 passes between an upper foraminous belt 49 and a lower foraminous belt 50 (See Figure 3) . While held 5 between the belts 49, 50, the raw bat 47 passes into the oven 14. As shown in Figure 3, the oven 14 is provided with heating means 52 in which the temperature can be controlled by a thermostat 53. The oven 14 is also provided with air circulating means such as a fan (not shown) that causes the hot air to circulate in the direction shown by the arrows 55 and 56. This hot air heats and melts the particles 33, 34 of the fiber-binder causing them to flow to the intersections of the fibers is and further causes them to cross-link, thereby hardening the fiber-binder. The resultant product is the finally fully cross-linked or partially cross-linked batt 58 depending on the temperature of the oven 14 and the length of time that the batt remained in the oven 14. In Figure 4 there is shown an alternative particle dispenser 12' which takes the place of the particle dispenser 12 of Figures 1, 2, and 3. In the dispenser 121 a raw batt 47 exists between two foraminous belts 60, 62. Streams of air, represented by the arrows 64, 66, are passed through the batt 47. These streams of air are laden with particles of fiber-binder. The particles loosely adhere to the fibers of the batt 47'. It has been found that fiber-binders of the present invention have a greater adherence to the fibers of the raw batt 47' than do the prior art thermoplastic fiber-binders.

As depicted in Figure 5, particles, such as the particles 33, 34 of uncured fiber- binder, are adhering to fibers 20, 20', 20" of the raw batt 47, 47'. In Figure 6, after heating, the particles, such as the particles 33, 34, have melted and have migrated to the intersections of the fibers 20, 20', 20". This heating has also caused the polyester resin of the fiber-binder to react with the cross-linking agent of the fiber-binder thus cross-linking this thermosetting composition. The bending resistance and resilience of the batt are directly proportional to the extent of cross-linking. A small amount of cross-linking gives a soft resilient batt. If the resin is fully reacted with the crosslinking agent, i.e., the fiber-binder is in the C-stage, the batt will have maximum firmness and strength. All other things being equal the extent of cross-linking can be controlled by the temperature and time of heating for cross-linking. Lower temperatures , and shorter times yield less cross-linking, while higher temperatures and longer times yield more cross-linking. Figure 7 illustrates the hot molding of batts of the present invention. Such batts can be hot-molded if the time and temperature of the heating step, Step III, is limited such that the cross-linking agent reacts with less than all the terminal groups of the polyester resin. In this case the resultant product will be a semi-cross-linked batt 47'". The semi-cross-linked batt 47" is placed between an open male mold 70 and an open female mold 72. The male mold 70 is provided with passages 74, 76, adapted to receive a heated fluid such as steam or hot oil. Similarly the female mold 72 has a fluid receiving passage. Either or both of the molds can be heated by any other convenient means such as electrical resistance heating.

As shown in Figure 8, the molds 70, 72 are closed causing the semi-cross-linked batt 47" to take the form of the molds 70, 72. Hot oil or steam under pressure is passed through the passages 74, 76, 78, heating the molds 70, 72, and thus heating the semi- cross-linked batt 47" to cross-linking temperature. This cross-linking temperature is above the melting point of the fiber-binder but below the scorching or melting point of the fibers thereby further reacting the cross-linking agent with the remaining terminal groups of the polyester resin. This converts the semi-cross-linked batt 47" into a fully cross-linked bat 47 in the form of shaped article 47 shown in Figure 9. Figures 12, 13, and 14 show the manner in which bending resistance is measured.

Figures 12 and 13 show an apparatus 88 comprising a scale 90, with a clamp 92 carried by a rotatable shaft 94 mounted parallel to the scale 90 about 20 cm (8 inches) above it. The batt 58 is positioned in the clamp 92 and held above and out of contact with the scale 90 as shown in Figures 12 and 13. To measure bending resistance, the shaft 94 is rotated one full turn as shown in Figure 14 and the highest reading on the scale 90 noted. In these tests the batt 58 has a width of 30 cm (12 inches) and a length of 30 cm (12 inches).

Examples

The invention will be better understood by reference to the following examples wherein all parts and percentages are by weight unless otherwise indicated. These examples are designed to teach those skilled in the art how to practice the present invention and represent the best mode presently known for carrying out the present invention.

Example 1

This example compares the prior art pads made with PVDC/PVC resin with a pad made from a polyester resin cross linked with TGIC. Both pads were cured at 350°F and had the same weight and resin content, as shown. The improvement in FLEX firmness is significant.

Example 2 This example is a polyester cross-linked with caprolactam blocked IPDI polymer

(isophoronediisocyanate), to produce a resin generally described as a urethane.

Example 3

Example 3 is a pad cross-linked with Primid®XL552, which is bis- N¹- dihydroxyethyl adipamide.

Example 4

Example 4 compares the prior art pad with one made from scrap powder paint consisting of a mixture of polyester cross-linked with TGIC, polyester cross-linked with IPDI (a urethane) and a polyester cross-linked with an epoxy resin. The mixture in this case is roughly 40% of IPDI cross-linked material, 20% of TGIC cross-linked material, and 40% of polyester cross-linked with epoxy resin.

Although the invention has been described in considerable detail with respect to certain preferred embodiments thereof, it will be understood that variations are within the skill of the art without departing from the spirit of the invention as described above and as defined in the appended claims.

Claims

What is Claimed Is:

1. A non- woven batt comprising fibers bonded with a fiber-binder, the binder comprising:

(iii) a solid polyester resin having terminal hydroxyl or carboxyl groups, and (iv) a coreactive effective amount of a cross-linking agent for reaction with the terminal groups of the polyester resin; wherein the fiber binder contains no formaldehyde or hydrochloric acid or compounds which production at an oven temperature of 232┬░C, and wherein the batt has a humidity resistance of over 100 hours measured by test 463PB-9-01, and wherein the fibers do not melt or decompose at temperatures below 100┬░C, and wherein the fiber-binder has a glass plate flow length of from about 15mm to about 150mm before being bonded to the fibers, and wherein the fiber-binder has an average particle size from about 1 to about 200 microns and wherein the non-woven batt containing the fiber bonding resin is compressed and heated to cause the fiber binder particles to melt and band the fibers together.

2. The bonded, non-woven batt of fibers of claim 1, wherein the solid resin is scrap powder paint.

3. The bonded, non- woven batt of fibers of claim 1, wherein the polyester fiber binder further comprises from about one to about 60% by weight of a particulate inorganic filler

4. The bonded, non-woven batt of claim 1, wherein the fiber-binder is free from solvents.

5. The bonded, non-woven batt of claim 1, wherein the fiber-binder is substantially anhydrous.

6. The bonded, non- woven batt of claim 1, which does not contain chlorine containing resins and which does not release hydrochloric acid.

7. A bonded, non- woven batt comprising fibers bonded with a fiber-binder, the binder comprising: (I) a solid polyester resin having polyester groups, and (ii) a coreactive effective amount of a cross-linking agent reacted with terminal groups of the polyester resin; wherein the batt is produced by a process comprising the steps of : I. providing a dry, solid, particulate, latent-curable, thermosetting, fiber-binder which is an intimate mixture of A. a solid polyester resin having: (a)terminal hydroxyl or acid groups; (b) a molecular weight above about 2000; (c) a glass transition temperature above about 40┬░C;

(d) a melting point above about 40┬░C, preferably about 70┬░; and

III. heating the raw batt to a cross-linking temperature above the melting point of the fiber-binder but below the scorching or melting point of the fibers thereby melting the fiber-binder whereupon the fiber-binder flows to intersections of the fibers and subsequently at least partially reacts the cross-linking agent with the terminal polyester groups of the polyester resin thereby converting the raw batt into a hot cured batt; and then

IV. cooling the hot cured batt.

8. The bonded, non-woven batt of claim 7, wherein the solid resin is scrap powder paint.

9. A process for preparing a bonded, non- woven, batt of fibers, the process comprising the steps of :

I. providing a dry, solid, particulate, latent-curable, thermosetting, fiber-binder which is an intimate mixture of A. a solid polyester resin having: (a) terminal hydroxyl or carboxyl groups;

(b) a molecular weight above about 2000; (c) a glass transition temperature above about 40┬░C; (d) a melting point above about 70┬░C; and

IV. cooling the hot cured batt.

10. The process of claim 9, wherein the solid resin is scrap powder paint.