EP0988948A1 - Method for making shaped objects from a vegetable raw material by injection-moulding - Google Patents

Abstract

The injection molding process, using a material which is primarily of vegetable origin, initially heats it to a viscous liquid state or a pulp, to be injected under pressure into the mold. The primary material is an oilcake of sunflower or rape seed which has oil extracted so that the oil content is ≤ 25 wt.%. The moisture content is set at 2-40%. The granules have an average dia. of 0.1-1.2 mm, and the protein content of the fibers is evenly distributed. The oilcake has a max. 2 wt.% of oil, as a result of the attrition of the sunflower or rape seeds. The material has a hydration of 2-15%, to be heated to a temp. of 110-200 degrees C, to be pressed into a cold mold or at a mold temp. of ≤ 65 degrees C. Where the material has a hydration of 20-40%, it is heated to a temp. of 30-100 degrees C and pressed into a hot mold with a temp. of 90-140 degrees C. The sunflower or rape seeds are used without husks. The oilcake is enriched with vegetable proteins. The granules have an average dia. of 0.2-0.7 mm with a cut dia. of 0.8 mm. The material is homogenized and oil extracted partially in a twin-screw extruder. The extruder, from upstream to downstream, has an injector (6,7) for water and/or an alcohol solvent, a crushing zone (Z2) with at least one kneading crusher (8), a zone of crushing pressure (Z3), a bleed (11,12) for the liquid phase, at least one reverse pitch module (10) to apply an axial compression to the solid material, and an extrusion opening (14) for the solid matter.

Description

The invention relates to a method of molding an object by injection of the type in which a raw material is brought by heating to the state of viscous or pasty liquid, it is injected under pressure into a mold and the hardened material is removed from the mold. The invention aims to take advantage of the performance of these injection processes (high rates, absence handling, various forms obtained) to manufacture objects which, while benefiting from durability and stability characteristics compatible with their function, are biodegradable, compostable and recyclable. Through "biodegradable" means that said object is capable of being degraded at least for the most part by natural microorganisms when put in the appropriate conditions, without release of toxic products for the ecosystem, and on a scale of a few weeks to a few months. Through "compostable" means an object which, divided, homogenized and mixed with organic matter and / or soil, provides a non-toxic nutritious substrate for plants. By "recyclable" is meant an object whose material can be reused to form an object of the same range.

Environmental constraints are increasing severe, in particular for disposable products (in particular packaging and packaging), and we are trying to manufacture these products by giving them a biodegradable and / or compostable and / or recyclable in order to prevent them become pollution or require expensive disposal treatments. Synthetic plastics generally meet the latter requirement but their recycling is expensive and requires prior sorting to separate the various types of materials, sorting which are not very compatible with the current lifestyle.

To limit these drawbacks, numerous studies have proposed to manufacture by injection objects in composite material using vegetable fibers such as wood, flax and hemp fibers, and incorporating these fibers into a thermoplastic synthetic matrix to obtain objects of good cohesion (GB-2 265 150). This solution does not solve entirely the problem of the destruction of objects after use, due the presence of the plastic matrix.

Some publications have proposed to inject extracts purified from plant material, especially soy protein extracts (US-5,523 293, "Schilling, Mechanical properties of biodegradable soy-protein plastics, J. Mater Res. Flight. 10, n ° 9, Sept. 1995, p.2197-2202 "). The essential defect of this type of techniques resides in its high cost coming mainly from the cost obtaining purified extracts (cost of protein extraction for examples of previous documents cited above). Such techniques do not the knowledge of the inventors, never implemented industrially fact that the proteins extracted have much more interesting outlets in other applications (especially food) that allow better recovery as the manufacture of packaging or packaging.

Furthermore, it should be noted, moreover, that certain residues ligno-cellulosic from oils extraction processes have been heat-pressed to give them cohesion and a certain resistance.

The present invention proposes to overcome the disadvantages of known methods and to indicate a new method allowing to manufacture by injection a biodegradable, compostable and recyclable object in remarkable savings conditions.

Another object of the invention is to manufacture an object which has good mechanical resistance, compatible with uses common (small packages or packaging such as cups, pots, small containers, small objects of everyday life ...).

• ledit tourteau est au moins partiellement déshuilé de sorte que sa teneur pondérale en huile est inférieure à 25 %,
• ledit tourteau est hydraté de façon à présenter un taux d'hydratation sensiblement compris entre 2 % et 40 %,
• ledit tourteau présente une répartition granulométrique telle que le diamètre médian D₅₀ de ses particules soit compris entre 0,1 mm et 1,2 mm,
• les particules des constituants protéique et fibreux dudit tourteau sont dispersées de façon sensiblement homogène.

To this end, the injection molding process targeted by the invention consists in heating a raw material to bring it to the state of a viscous or pasty liquid, in injecting it under pressure into a mold and in removing the mold from hardened material. According to the present invention, a raw material of sunflower or rapeseed meal having the following characteristics is used as the raw material for carrying out the injection:

• said cake is at least partially de-oiled so that its oil content by weight is less than 25%,
• said cake is hydrated so as to have a hydration rate substantially between 2% and 40%,
• said cake has a particle size distribution such that the median diameter D ₅₀ of its particles is between 0.1 mm and 1.2 mm,
• the particles of the protein and fibrous constituents of said cake are dispersed in a substantially homogeneous manner.

"Sunflower or rapeseed meal" means the residue solid oil extract from whole sunflower or rapeseed or shelled, whatever the means of extraction (pressing, extraction solvent ...), this oil extraction can be total or partial but lowering the oil content by weight of the product below the above-mentioned threshold of 25%.

By "median diameter D ₅₀ " is meant a diameter such that 50% of the particles by weight pass through a vibrating screen having a mesh of side equal to said diameter. (All particle size measurements are made on dry matter). (All weight contents are expressed as a percentage relative to the weight of dry matter; the hydration rate is expressed relative to the total matter).

Experiments have shown that from of a raw material consisting of sunflower meal or brown crab rapeseed prepared appropriately to meet the conditions previously defined, it was possible to achieve, by a conventional injection process, products of various forms, benefiting from an excellent cohesion and quality of resistance of the order of that of ordinary objects such as small containers, pots, cups, packaging, packaging ... without the need to add a any adjuvant. Thus, the method of the invention makes it possible to benefit from the high rates of injection processes and their flexibility of implementation to get very cheap items from a raw material natural, abundant, without addition of extracts, finished or semi-finished products, synthetic or natural products. It is completely unexpected that such a residue sunflower or rapeseed plant, very heterogeneous and currently considered as a by-product of little value (used only in food animal to ensure a low energy value), allows implementing under satisfactory conditions an injection process for manufacturing an object of equivalent quality to that of injected plastic objects synthetic. This remarkable result is explained a posteriori by the inventors by the composition of sunflower or rapeseed meal, which contains proteins which are suitable for injection and fibers which are able to form a homogeneous whole with the protein matrix (without interfacial discontinuity despite the difference in chemical nature of these constituents). The water of hydration of the cake seems necessary to promote the transition to viscous or pasty state of the raw material under thermal action

Furthermore, it could be noted that the residual oil from oil cake has a rather unfavorable effect on the qualities of the objects obtained, in particular on their mechanical properties, and advantageously a sunflower or rapeseed meal exhausted in oil, that is to say containing at most 2% oil, especially from crushing and solvent extraction of seeds sunflower or rapeseed. We limit or suppress the forces of hydrophobic repellency which tends to oppose association fiber / protein.

According to a first mode of implementation, called injection hot mold, using a cake having a substantially hydration rate between 20% and 40%, and before injection, said cake is heated to a temperature between 30 ° C and 100 ° C, then sent to a mold heated to a temperature between 90 ° C and 140 ° C. This injection mode is of relatively slow implementation and its optimization requires a rate high hydration, to achieve a viscous state at low temperature or cake cake allowing its injection into the mold in good conditions.

According to another mode of implementation, called injection cold mold, using a cake having a substantially hydration rate between 2% and 15%, and, before injection, said cake is heated to a temperature between 110 ° C and 200 ° C, then sent under pressure to a mold cold or with a temperature below 65 ° C. This injection mode is commonly used for synthetic plastics and allows very high rates. Tests have shown that in this mold injection cold, a cake hydration rate appreciably between 5% and 15% gives good results, in particular avoiding the formation of pockets of vapor and reducing the shrinkage of material on cooling, which leads to more precise shapes.

If we seek to increase the mechanical performance of objects obtained, it is possible to use a meal of sunflower seeds or shelled rapeseed, which naturally contains a higher proportion of proteins. Of course, it is also possible, in certain applications, to use a sunflower or rapeseed meal enriched with vegetable proteins by addition in order to further increase these mechanical performances at the cost of cost increase.

In the process of the invention, the sunflower or rapeseed meal is subjected beforehand to a mechanical treatment of division and homogenization to give it the particle size distribution previously defined; preferably, this treatment is carried out so that the median diameter D ₅₀ of the particles is substantially between 0.2 mm and 0.7 mm, and the cut-off diameter D ₉₅ is less than or equal to 0.8 mm. By "cut-off diameter D ₉₅ " is meant a diameter such that 5% of the particles by weight are stopped by a vibrating screen having a mesh of side equal to said diameter.

Such a distribution can in particular be obtained by passage of the cake in a twin-screw device which ensures a division, a homogenization and, where appropriate, partial or complete de-oiling thereof, capable of leading to a better quality of the objects injected (better mechanical resistance, less defects and shrinkage of material). The twin-screw device can optionally be chosen to ensure complete oil removal of oil cake (without any other oil extraction operation) or, on the contrary, be coupled downstream of a conventional extraction press ensuring de-oiling or part of this one.

The method of the invention makes it possible to manufacture objects biodegradable, compostable and recyclable models, essentially made a protein matrix reinforced by plant fibers oriented according to one or preferred directions and having a substantially flexural strength between 3 and 30 megapascals.

The following examples are intended to illustrate the process of the invention.

• la figure 1 est une représentation longitudinale symbolique dudit dispositif bi-vis,
• la figure 2 en est une coupe transversale par un plan A,
• la figure 3 est un schéma symbolique de la presse à injecter utilisée dans les exemples.

In Examples 1 and 3, the cake after oil removal by twin-screw or traditional pressing is subjected to a preliminary preparation treatment in a twin-screw device of specific configuration; this twin-screw device and the injection device allowing the injection to then be carried out are shown diagrammatically in the accompanying drawings; on these drawings:

• FIG. 1 is a symbolic longitudinal representation of said twin-screw device,
• FIG. 2 is a cross section thereof through a plane A,
• Figure 3 is a symbolic diagram of the injection molding machine used in the examples.

The twin-screw device shown diagrammatically in Figures 1 and 2 is used to prepare the oil cakes after oil removal; this device is obtained from modules marketed by the Company "CLEXTRAL" (registered trademark) under the general reference "BC45". Each module includes a double wall tubular enclosure 1 and 2 which allows a thermal regulation of the core of the enclosure where the active organs are housed. Some modules are of the type comprising two identical co-penetrating screws, others of the type comprising shear mixers composed of discs bilobes or mixing discs. The various modules are rotated in synchronism by an electric motor 3 making it possible to obtain a speed of rotation of its output shaft up to 700 rpm. In the examples, the rotational speed chosen varies from 100 rpm to 200 rpm.

• une zone de convoyage et mise en pression Z₁, comprenant une trémie 4 d'alimentation en tourteaux, des modules de bi-vis à pas direct décroissants tels que 5, et un conduit 6 doté d'une pompe 7 pour l'injection d'eau et/ou d'un solvant alcoolique,
• une zone de cisaillement Z_2, comprenant un ou des malaxeurs à disques bilobes tels que 8,
• une zone d'écrasement et mise en pression Z₃, combinant des modules d'écrasement constitués par des modules de bi-vis à pas direct tels que 9, avec un pas décroissant d'amont vers l'aval, un ou des modules de bi-vis à pas inversés 10 pour réaliser une compression axiale des matières,
• des moyens de soutirage de la phase liquide situés au niveau de la zone Z₃ et combinant un filtre 11 et une sortie de liquide 12 (mis en service dans le cas où un déshuilage complémentaire des tourteaux est recherché),
• et une zone terminale de recueil des matières solides Z₄, comprenant des modules de bi-vis à pas direct 13 et une sortie 14 des matières (tourteaux prêts à l'injection).

The device essentially comprises the following functional areas (from upstream to downstream):

• a conveying and pressurizing zone Z ₁ , comprising a hopper 4 for supplying cake, decreasing twin-screw modules with direct pitch such as 5, and a conduit 6 provided with a pump 7 for the injection of water and / or an alcoholic solvent,
• a shear zone Z _2, comprising one or more two-lobe disc mixers such as 8,
• a crushing and pressurizing zone Z ₃ , combining crushing modules constituted by twin screw modules with direct pitch such as 9, with a decreasing pitch from upstream to downstream, one or more modules twin-screw with inverted pitch 10 to achieve axial compression of the materials,
• means for withdrawing the liquid phase situated at the level of zone Z ₃ and combining a filter 11 and a liquid outlet 12 (put into service in the case where additional oil removal from the oil cakes is sought),
• and a terminal zone for collecting the solid materials Z ₄ , comprising direct screw twin-screw modules 13 and an outlet 14 for the materials (oil cakes ready for injection).

The injection molding machine symbolized in Figure 3 is a press 90t, comprising a cake feed hopper 15, an endless screw conveying and pressurizing 16, a pressurized injection nose 17 and a mold 18 of known type, with opening by jacks.

EXAMPLE 1: Composition of the raw material used

In this example, two-screw sunflower meal is used, the composition of which is as follows: % hydration rate % minerals / MS % protein / DM % lipids / DM % cellulose / MS % lignin / MS % hemicellulose / MS % phenolic compounds / MS 10.8 5.2 26.7 25 16.7 3.9 14.9 4.3

Preparation of the material:

The hydration and homogenization of the material are performed using the bi-screw device described (Figures 1 and 2).

The screw rotation speed is equal to 100 revolutions per minute and the device temperature is regulated and maintained at 100 ° C. The flow of raw material injected at the head is close to 24 kg / h.

About 9 l / h of water are injected through line 6 at the level of zone Z ₁ .

The hydrated material produced has a final moisture content of 24%, an equivalent median diameter D ₅₀ of 0.35 mm (dry measurement) and a cut-off diameter D ₉₅ of 0.8 mm. It is in the form of a homogeneous friable paste.

Injection :

The injection is carried out using the injection press described figure 3.

• la température maximum dans la vis 16 (Tv),
• la température du moule (Tm),
• la pression limite d'injection (P1i),
• les pression de maintien (Pm1, Pm2),
• la durée des pressions de maintien (t1, t2),
• la durée de solidification (ts).

The injection and molding parameters are as follows:

• the maximum temperature in screw 16 (Tv),
• the mold temperature (Tm),
• the injection limit pressure (P1i),
• the holding pressures (Pm1, Pm2),
• the duration of the holding pressures (t1, t2),
• the solidification time (ts).

For the example treated, the value of these parameters is given in the following table: Tm (° C) Tv (° C) P1i (b) Pm1 (b) Pm2 (b) t1 (s) t2 (s) ts (s) 103 50 40 30 30 25 50 90

The formed parts are standardized test pieces of dumbbell type lA (ISO 527) used for the measurement of tensile strength, rectangular pieces 60x10x4mm used for resistance measurements in bending and 90mm diameter discs.

Maturation is carried out at 50 ° C for 12 hours.

The shrinkage observed during maturation is 1.4% over the large dimension of the rectangular part.

The mechanical characteristics of the parts, measured on a TAXT2 Texturometer (Rhéo) after conditioning at 25 ° C and 60% humidity for 24 h are presented in the following table: Flexion (Mpa) Traction (Mpa) Resistance Young's module Resistance Young's module 3.5 ± 0.5 497 ± 40 1.2 ± 0.17 110 ± 3

EXAMPLE 2 : Composition of the raw material

In this example, two-screw expression cake is used, the composition of which is as follows: % hydration rate % minerals / MS % protein / DM % lipids / DM % cellulose / MS % lignin / MS % hemicellulose / MS % phenolic compounds / MS 10.8 5.2 26.7 25 16.7 3.9 14.9 4.3

Preparation of the material

In this example, the material does not undergo additional hydration or homogenization. It has a humidity rate of 9%, a D ₅₀ of 0.35 mm and a D ₉₅ of 0.8 mm. It comes in a powder form.

Injection

The shaping is carried out using the injection press described (Figure 3).

For the example treated, the value of the injection parameters is given in the following table: Tm (° C) Tv (° C) P1i (b) Pm1 (b) Pm2 (b) t1 (s), t2 (s), ts (s) 40 190 30 30 20 35

The parts formed are the same as those described in Example 1. Maturation is done in the same way as in Example 1. The shrinkage during maturation is very low and cannot be assessed reliable.

The flexural strength of the parts, measured on a TAXT2 texturometer (Rheo) after conditioning at 25 ° C and 60% humidity is presented in the following table: Resistance (MPa) Young's modulus (MPa) 5.12 1147

EXAMPLE 3 : Composition of the raw material :

In this example, oil cake exhausted from the crushing of sunflower seeds is used, the composition of which is as follows: % hydration rate % minerals / MS % protein / DM % lipids / DM % cellulose / MS % lignin / MS % hemicellulose / MS % phenolic compounds / MS 10.0 7.0 35.6 1.0 22.3 5.2 18.5 5.7

The D ₅₀ of the material is equal to 0.65 and its D ₉₅ to 2.

Mechanical preparation and hydration of the material

Hydration, homogenization and division of matter are made using a twin-screw device with the profile illustrated in Figures 1 and 2.

The screw rotation speed is 200 revolutions per minute and the device temperature is regulated and maintained at 100 ° C. The flow of raw material injected at the head is close to 23 kg / h.

About 3 l / h of water are injected into line 6 at the level of zone Z ₁ .

The hydrated material produced has a final moisture content of 5% and, when dry, a D ₅₀ of 0.4 mm and a D ₉₅ of 0.7 mm. It comes in the form of a crumbly paste.

Injection:

The shaping is carried out using the injection press described.

For the example treated, the value of the injection molding parameters is given in the following table: Tm (° C) Tv (° C) P1i (b) Pm1 (b) t1 (s) ts (s) 65 115 110 100 5 13

The formed parts are similar to those described in Example 1.

Maturation is done in the same way as in Example 1.

The shrinkage observed during maturation is 1.7% over the length of the rectangular part and 3% across its width.

The mechanical flexural characteristics measured on TAXT2 Texturometer (Rhéo) after conditioning at 25 ° C and 60% humidity for 24 h are presented in the following table: Resistance (MPa) Young's modulus (MPa) 14.1 2156

EXAMPLE 4 : Composition of the raw material:

In this example, oil cake exhausted from the crushing of sunflower seeds is used, the composition of which is as follows: % hydration rate % minerals / MS % protein / DM % lipids / DM % cellulose / MS % lignin / MS % hemicellulose / MS % phenolic compounds / MS 10.0 7.0 35.6 1.0 22.3 5.2 18.5 5.7

The D ₅₀ of the material is equal to 0.65 and its D ₉₅ to 2.

Mechanical preparation of the material

Hydration, homogenization and division of matter are made using a twin-screw device with the profile illustrated in Figures 1 and 2.

The screw rotation speed is 200 revolutions per minute and the device temperature is regulated and maintained at 100 ° C. The flow of raw material injected at the head is close to 25 kg / h.

About 0.5 l / h of water is injected into line 6 at the level of zone Z ₁ .

The material produced has a final moisture content of 2% and, when dry, a D ₅₀ of 0.4 mm and a D ₉₅ of 0.7 mm. It comes in the form of a crumbly paste.

Injection:

The shaping is carried out using the injection press described.

For the example treated, the value of the injection molding parameters is given in the following table: Tm (° C) Tv (° C) P1i (b) Pm1 (b) t1 (s) ts (s) 56 115 110 40 5 13

The formed parts are similar to those described in Example 1.

Maturation is done in the same way as in Example 1.

The shrinkage observed during maturation is 2.9% over the length of the rectangular part and 3.8% across its width.

The mechanical flexural characteristics measured on TAXT2 Texturometer (Rhéo) after conditioning at 25 ° C and 60% humidity for 24 h are presented in the following table: Resistance (MPa) Young's modulus (MPa) 21.3 2531

Claims (10)

1 / - Process for molding an object by injection, in which a raw material is brought by heating to the state of viscous or pasty liquid, this is injected under pressure into a mold and the material is removed from the mold hardened, characterized in that a raw material of sunflower or rapeseed meal having the following characteristics is used: said cake is at least partially de-oiled so that its oil content by weight is less than 25%, said cake is hydrated so as to have a hydration rate substantially between 2% and 40%, said cake has a particle size distribution such that the median diameter D ₅₀ of its particles is between 0.1 mm and 1.2 mm, the particles of the protein and fibrous constituents of said cake are dispersed in a substantially homogeneous manner. 1 / Injection method according to claim 1, characterized in that one uses a sunflower or rapeseed meal exhausted in oil, containing at most 2% oil, in particular from the crushing of sunflower or rapeseed seeds. 2 / - Injection method according to one of claims 1 or 2, characterized in that one uses a cake having a hydration rate substantially between 2% and 15%, said cake being heated to a temperature between 110 ° C and 200 ° C and sent under pressure in a cold mold or with a temperature below 65 ° C. 3 / - Injection method according to one of claims 1 or 2, characterized in that one uses a cake having a hydration rate substantially between 20% and 40%, said cake being heated to a temperature between 30 ° C and 100 ° C and sent under pressure in a mold heated to a temperature between 90 ° C and 140 ° C. 4 / - Injection method according to one of claims 1, 2, 3 or 4, characterized in that one uses a meal of shelled sunflower or rapeseed seeds. 5 / - Injection method according to one of claims 1, 2, 3 or 4, characterized in that one uses a sunflower or rapeseed meal enriched with vegetable proteins. 6 / - Method according to one of the preceding claims, characterized in that an oil cake having a particle size distribution is used such that the median diameter D ₅₀ of its particles is between 0.2 mm and 0.7 mm, and the cut-off diameter D ₉₅ is less than or equal to 0.8 mm. 7 / - Method according to claim 7, characterized in that one uses a divided cake, homogenized and at least partially deoiled by passage of sunflower or rapeseed seeds in a twin-screw device. 8 / - Process according to claim 8, in which a twin-screw device is used comprising, from upstream to downstream, where appropriate means (6, 7) for injecting water and / or an alcoholic solvent , a shear zone (Z ₂ ) comprising at least one shear mixer (8), a crushing and pressurization zone (Z ₃ ), means (11, 12) for withdrawing the liquid phase, at least an inverted step module (10) for achieving axial compression of the solid materials, and an outlet (14) for the solid materials. 9 / - Molded biodegradable, compostable and recyclable object, capable of being manufactured by implementing an injection process according to one of claims 1 to 9, characterized in that it essentially consists of a protein matrix reinforced by vegetable fibers oriented in one or more preferred directions and in that it has a flexural strength substantially between 3 and 30 megapascals.

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