EP1885809A2

EP1885809A2 - Sizing composition for glass fibre granules with a high glass content

Info

Publication number: EP1885809A2
Application number: EP06794392A
Authority: EP
Inventors: Yohann Barnaud; Jean-Philippe Gasca
Original assignee: Saint Gobain Vetrotex France SA
Current assignee: Saint Gobain Adfors SAS
Priority date: 2005-05-04
Filing date: 2006-05-02
Publication date: 2008-02-13
Also published as: FR2885362A1; US20080254290A1; WO2007000517A3; KR20080004573A; FR2885362B1; CN101171314A; ZA200709426B; JP2008540306A; BRPI0610729A2; WO2007000517A2; CN101171314B; TW200710144A

Abstract

The invention relates to a sizing composition for glass fibres comprising the following components as expressed in percentages by weight of solid matter, namely: 10 to 99 % of at least one copolymer that is selected from among copolymers of vinyl acetate and ethylene or acrylic or methacrylic acid, 1 to 40 % of at least one coupling agent, and 0 to 90 % of polypropylene grafted by at least one unit derived from at least one monomer containing one or more functions that can react with the coupling agent. The glass fibres obtained are intended to be used to form glass fibre granules having a high glass content for the production of composite parts comprising a thermoplastic matrix that is reinforced with cut glass fibres by means of injection moulding.

Description

SINGING COMPOSITION FOR GRANULES OF GLASS WIRES A

HIGH GLASS CONTENT

The invention relates to a sizing composition for glass strands that can be used to form granules with a high glass content. These granules are intended more particularly to manufacture molded parts made of thermoplastic material reinforced with glass threads known under the name

TPA (abbreviation of "reinforced thermoplastic").

Such parts can be manufactured in different ways, in particular by the technique of "injection molding".

In general, the injection molding of TPA parts is carried out in an installation comprising an injection press associated with a mold. The injection press comprises an assembly formed of a heated sheath and an injection screw, generally of "single-screw" type, surmounted by a feed hopper made of thermoplastic material and glass threads.

The thermoplastic material and the glass threads are introduced separately into the hopper and then mixed into the sleeve-screw assembly where the thermoplastic material is melted and plasticized (i.e. transformed into a viscous injectable material) and the same time the glass son are impregnated with the thermoplastic material and dispersed therein.

The resulting thermoplastic-glass mixture is then injected into the mold. The injection takes place in three phases:

filling (or injection): the mixture pushed by the injection screw serving as a piston fills the cavity of the mold. If necessary, a pressure can be applied on the mold at the end of filling,

- compacting: the mixture is kept under pressure during cooling,

- Cooling: the polymer is frozen and the TPA piece is ejected when its rigidity is sufficient. The aforementioned molding technique does not allow the use of conventional cut glass yarns directly in the hopper; the yarns intermingle and form entanglements that quickly block the flow of granulated thermoplastic material and threads to the injection screw. To ensure a proper implementation, the glass son are therefore converted into granules.

Granules are known in which the glass threads of variable length are associated with thermoplastic material. The "short" wire granules, less than 1 mm long, are formed from thermoplastic material and cut glass son in an extruder equipped with a "twin-screw" type screw, and cutting of the rod formed into granules of the desired length. The high shear induced by this type of extrusion screw makes it possible to separate the glass filaments and consequently to sufficiently impregnate them with the thermoplastic material and to disperse them correctly therein. Nevertheless, the level of reinforcement is not very high because of the short length of the glass strands.

The "long" glass fiber granules, typically of more than 6 mm, are obtained by passing one or more continuous glass strands, for example in the form of a roving, in a die fed with the molten thermoplastic material and then cutting the cooled glass wire to the required length. This type of granulate, known as

"Pellet" in English, contains glass threads of the same length as the pellet; it gives the castings better mechanical properties. Other granules with a high glass content, greater than 90% by weight, are known from WO 03/097543. However, these granules are not entirely satisfactory because the glass son they contain do not disperse correctly in the thermoplastic material to be reinforced. The presence of yarns within the matrix affects the quality of the molded parts whose mechanical performance is reduced.

The invention is particularly interested in the latter type of granules with a high glass content.

The glass strands that make up these granules consist of a multitude of individual filaments (of the order of 1,000 to 100,000 filaments per basic thread), of 5 to 24 μm in diameter, for example from 10 μm to 17 μm. μm and length generally not exceeding 30 mm.

In general, the glass filaments are coated with a sizing: in addition to the protection against abrasion that it brings to the filaments during the elaboration of the son, it is important that the size also confers additional properties specific to the intended application.

The size must be able to bind the filaments together to give a wire capable of being cut into elements of identical length with a quantity of "fines", that is to say of smaller particles, which is the weakest possible.

Because the transport is most often carried out pneumatically, the sizing must also provide the glass fiber granules with the capacity to withstand the major mechanical stresses resulting from the friction of the wires with each other and against the walls of the transport pipes which cause a bursting of the threads and the release of the filaments of glass that constitute them (we speak of "filamentisation"). The filaments then form "flock" which obstructs the pipes.

The sizing must further contribute to bond the glass strands during granulation to form high density granules which can flow easily into the metering device and into the feed hopper of the injection screw. Indeed, most metering devices are gravimetric metering based on a constant flow that operate by opening traps releasing granules, the opening time being calculated and adjusted as and when metered dosages. It is therefore important that the granule shape factor defined by the ratio of the length to the diameter remains constant, that the glass threads remain sufficiently cohesive and that they can not be released and become entangled forming "bridges" which disturb or block the flow of materials to the injection screw. The object of the present invention is to provide a sizing composition capable of coating glass yarns to form chopped yarn granules, in particular suitable for injection molding, which have a high glass content and a better dispersion in the matrix. thermoplastic to reinforce.

The sizing composition which is the subject of the invention is an aqueous composition comprising the constituents below, in the following weight contents expressed as percentages of the solids:

10 to 99% of at least one copolymer chosen from copolymers of ethylene and of vinyl acetate or of acrylic or methacrylic acid - 1 to 40% of at least one coupling agent

- O to 90% polypropylene grafted with at least one unit derived from at least one monomer containing one or more functions that can react with the coupling agent. The copolymer makes it possible to modulate the speed of impregnation of the threads with the thermoplastic material. It results from the polymerization of ethylene and at least one monomer selected from vinyl acetate, acrylic acid and methacrylic acid.

Advantageously, the copolymer has an ethylene content of at least 50% by weight, preferably at least 65% and more preferably at least 80%, which makes it possible to have good compatibility with the thermoplastic matrix at to reinforce.

The melting point of the copolymer is generally less than

30 ° C at the melting point of the material to be reinforced, preferably at least 50 ° C. In general, when the material to be reinforced is polypropylene, the copolymer has a melting point of less than 160 ° C., preferably less than 140 ° C. and advantageously of the order of 110 ° C.

The coupling agent makes it possible to hang the size on the surface of the glass filaments. The coupling agent is generally chosen from silanes such as gamma-glycidoxypropyltrimethoxysilane, gamma-acryloxypropyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, vinyltrimethoxysilane, phenylaminopropyltrimethoxysilane, styrylaminoethylaminopropyltrimethoxysilane or terbutylcarbanoylpropyltrimethoxysilane, and siloxanes. titanates, zirconates and mixtures of these compounds. Preferably, the silanes are chosen, advantageously the aminosilanes.

The grafted polypropylene according to the invention comprises at least one side chain bonded to the polypropylene main chain, the side chain being a unit derived from at least one monomer containing one or more functions that can react with the coupling agent. Preferably, the monomer is chosen from vinyl monomers and monomers carrying at least one alcohol, carboxylic acid, acid anhydride, especially carboxylic acid, amide or epoxide functional group. The degree of grafting of the polypropylene (ratio of the mass of grafted monomer to the weight of the graft polymer x 100) is between 0.2 and 8%, preferably between 0.5 and 5%.

Advantageously, the polypropylene is grafted with maleic anhydride. As a general rule, the maleic anhydride content in the grafted polypropylene ranges from 0.2 to 6%, preferably from 0.5 to 4%.

The melting point of the grafted polypropylene is generally greater than the melting point of the copolymer according to the invention described above.

The sizing composition obtained in the context of the invention may be in the form of a solution, suspension, dispersion or aqueous emulsion. Most often, the sizing composition is an emulsion.

Preferably, the sizing composition comprises the constituents below, in the following weight contents expressed as percentages of solids:

- 40 to 90% of at least one copolymer of ethylene and vinyl acetate or acrylic acid

5 to 20% of at least one coupling agent, preferably a silane and advantageously an aminosilane-10 to 60% grafted polypropylene, preferably with maleic anhydride.

The sizing composition may further comprise one or more components (hereinafter referred to as "additives").

Thus, the composition may comprise at least one film-forming agent chosen from polyurethanes, epoxies, polyesters and polyvinyl acetate. The content of film-forming agent may be up to 40% by weight of the sizing composition, preferably up to 10%.

The composition may also comprise, as additive, at least one surfactant or lubricant which helps to protect the filaments from abrasion and contributes to limiting the formation of flock during fiber drawing and wire cutting. The surfactant or lubricant is chosen from fatty acid esters such as decyl laurate, isopropyl palmitate, cetyl palmitate, isopropyl stearate, ethylene glycol adipate or trimethylolpropane trioctanoate. , and alkoxylated derivatives, especially ethoxylated derivatives of these esters, glycols derivatives such as polyethylene glycols or polypropylene glycols, optionally containing alkoxy groups, especially ethoxy, and mixtures of these compounds. Still as additives, the sizing composition may include an antistatic agent such as a quaternary ammonium salt.

The sizing composition may further comprise as an additive an anti-foaming agent, for example a polyalkylsiloxane such as polydimethylsiloxane. Preferably, the content of each of the abovementioned additives, except for the film-forming agent, does not exceed 3% by weight of the composition, the total content of these additives remaining less than 5%.

The sizing composition generally has a solids content of between 2 and 20%, preferably 4 and 15% and advantageously of the order of 10%.

The application of the sizing composition according to the invention to the glass filaments is carried out under the usual conditions known in the art. The threads of molten glass flowing from orifices arranged at the base of one or more dies are drawn in the form of one or more plies of continuous filaments, and then the filaments are gathered in one or more threads. The deposition of the size is performed on the filaments being stretched under the die.

The sized yarns, which constitute another object of the invention, are generally collected in the form of windings on rotating supports or are cut before collection by a member also serving to stretch them, most often disposed under the Faculty. The son obtained can thus be in different forms after collection, for example in the form of continuous yarn coils (cakes, rovings comprising a thread or several basic threads ("roving" assembled), "cops", etc. ) or chopped wires. The glass filaments constituting these threads have a diameter that can vary to a large extent, most often from 5 to 30 μm, preferably 8 to 20 μm.

They can be made of any glass, for example E, C, AR

(alkali-resistant) or with reduced boron content (less than 5%). The base yarns generally consist of 100 to 10,000 filaments, preferably 200 to 5,000, and preferably of the order of 1,000.

In general, the amount of sizing coating the glass son does not exceed 2% of the weight of the yarn and preferably is between 0.2 and 1.8%, and preferably between 0.5 and 1.5% .

The size coating the glass son has the particular that it softens at a lower temperature than the melting temperature of the material to be reinforced. Thus, under molding conditions, when the mixture of glass fiber and thermoplastic granules penetrates into the injection mono- screw, the size begins to flow before the thermoplastic material, which makes it possible to have a kneading effective material and a homogeneous distribution of son in the mixture to be injected.

In general, the softening of the size occurs at a temperature a few degrees Celsius higher than the melting temperature of the sizing compound having the lowest melting point, and at least 10 ° C lower, preferably at least 20 ° C and preferably at least 50 ° C at the melting temperature of the thermoplastic material to be reinforced.

The sized glass strands, which constitute another object of the invention, are used to form granules of cut glass strands with a high glass content.

The granules can be obtained according to any method known to those skilled in the art, in particular described in WO-A-96/40595, WO-A-98/43920, WO-A-01/05722 and WO-A-03/097543. . For example, the granules can be obtained by the process of cutting the glass strands to a length of between 6 and 30 mm, preferably directly under the spinneret as indicated above, and subjecting them to stirring in a suitable device. in order to agglomerate them. Under these conditions, the cut son are wet and generally contain 5 to 25% by weight of water.

The cut glass yarns to which, if appropriate, water has been added so as to have a water content of between 10 and 25% by weight, are treated in a brewing apparatus for a sufficient period of time up to obtaining granules containing at least 50% by weight of glass. The granules are then dried to remove water.

Advantageously, additives may be introduced during the stirring in a proportion not exceeding 3% of the total weight of the mixture. The additives are chosen from the coupling agents with the matrix to be reinforced, for example polypropylene grafted with maleic anhydride, the anti-aging agents making it possible to improve the heat resistance or the light resistance, the fillers, for example the carbon black.

The dried granules are composed of juxtaposed cut threads and have a length substantially equal to that of the cut glass starting threads, from 6 to 30 mm, preferably from 8 to 25 mm and advantageously from 9 to

15 mm. The diameter of the granules is generally between 0.5 and 4 mm, preferably 1 and 3 mm.

The granules have a glass content ranging from 95% to 99.8% by weight, preferably 98 to 99.5%.

The granules have a loss on ignition of less than 2% by weight, preferably less than 1.8%, and preferably ranging from 0.5 to 1.5%.

The granules can be used for the reinforcement of thermoplastic materials such as polyolefins, for example polyethylene and polypropylene, polyamides, polyalkylene terephthalates, for example PET polyethylene terephthalate and PBT polybutylene terephthalate, styrene polymers, for example acrylonitrile-butadiene-styrene (ABS), phenylene polysulfide PPS, polycarbonates and polyacetals, for example polyethylene oxide POM. Polypropylene is particularly preferred.

In general, the glass content in the final molded part is between 10 and 60%, advantageously 20 and 30%

Because of their high glass content, the granules obtained from the glass strands coated with the composition according to the invention can be used in combination with any thermoplastic matrix. This is an advantage over known injection molding granules which contain a substantial amount of thermoplastic material (at least 30 and up to 80% by weight depending on the type of granule) which may be some incompatibility with the material to reinforce. The following examples illustrate the invention without limiting it.

EXAMPLES 1 to 12 a) Preparation of the aqueous composition An aqueous sizing composition is prepared comprising the following compounds, in the weight contents given in Table 1, in% of the solids:

ethylene-vinyl acetate copolymer (EVA): marketed under the reference "EVA X ^® -28" by MICHELMAN; weight content of ethylene: 82%;

- ethylene-acrylic acid (EAA) sold under the reference ^"® Michem Prime 4983R" by Michelman; weight content of ethylene: 80%; weight average molecular weight: 8400; acid number: 156 - - gamma-aminopropyltriethoxysilane (silane): sold under the reference "Silquest ^® A-1 100" by GENERAL ELECTRIC;

- maleic anhydride grafted polypropylene (PPgMAH) sold under the "Michem ^® 43040» Reference by Michelman; grafting rate: 4% by weight; acid number: 45, weight average molecular weight: 9100;

- polyurethane (PU): sold under the "Baybond ^® PU401" reference by BAYER.

The preparation of the sizing composition is carried out as follows: The ethoxy groups of the silane ^{(3) are} hydrolyzed in deionized water kept stirring, and then the other constituents are added, still with stirring. The final pH is of the order of 10.

The weight content of solids in the sizing composition is equal to 10%. TABLE 1

b) obtaining the sized threads

The sizing compositions are used to coat, in a known manner, glass filaments E of about 17 μm in diameter drawn from glass threads flowing from the orifices of a die which are gathered together into 500 filament yarns. each.

EXAMPLES 14 TO 26-

The glass strands of Examples 1 to 13 are cut to an average length of 12 mm ± 1 mm and granulated in the granulation device described in the patent application WO 03/097543. The granules have a length of 12 mm ± 1 mm, a diameter of 2.5 mm, a density of 0.8 and a glass content greater than 98%.

The granules obtained are analyzed under the following conditions: the quantity of fines, that is to say of rods or of free glass filaments, is measured on a sample of 500 g of granules placed in a hopper whose chute of outlet is located 4 mm from a vibrating corridor allowing the flow and a homogeneous spreading of the granules. The fines are collected in a trap located above the vibrating corridor, by means of a suction device. The quantity of fines, expressed in mg / kg, is measured on the granules before and after the transport test (see following paragraph).

the quantity of flock after the pneumatic transport of the granules (transport test) is measured as follows: 2 kg of granules contained in a storage tank are sucked through a critical circuit up to the pneumatic injection hopper. a conventional injection press. The formed filament wad is collected on the filter of the pneumatic hopper and weighed. The amount of flock is expressed in mg / kg.

the granules are subjected to a PSI (Pneumatic Stress Integrity) test representing a pneumatic transport of the granules under high pressure under more severe stress conditions than the current industrial conditions. 50 g of granules are rotated in a stainless closed circuit at a pressure of 5 bar (0.5 MPa) for 45 seconds. The granules are recovered and sieved to recover the flock. The percentage of flock is given as a function of the initial mass of granules.

- the loss on ignition, in percentage, is measured under the conditions of ISO 1887,

- the flow of the granules or fibers, expressed in seconds / kilogram, is measured as follows: the product (5 kg) is placed in a hopper whose discharge orifice is located 28.5 mm from a corridor Vibrating flow with an amplitude of 1 mm.

The characteristics of the granules are given in Table 2.

TABLE 2

The granules of Examples 14 to 26 have a flowability of less than 15 s / kg, compatible with use in an injection molding device.

The granules according to the invention have good mechanical strength properties during transport. In particular, the granules of Examples 14 to 20 and 22 to 24 have a smaller amount of fines before and after the pneumatic transport, and less fuzz under the conditions of the injection (transport test) and under more severe conditions ( PSI test) than the granules of Examples 25 and 26 compared. The very low percentage of flock obtained with the examples according to the invention, reduced by a factor of 10 and 30 compared with Examples 25 and 26 respectively, reflects a high integrity of the glass strands due to the size. The granules of Example 21 have intermediate strength properties compared to comparative examples which remain acceptable for the intended application. By way of comparison, it is specified that glass threads coated with the size of Example 13 cut (length: 12 mm, loss on ignition: 0.75%), non-granulated (density: 0.4), can not be analyzed under the conditions of the tests mentioned: the wires become entangled rapidly and form "bridges" which block the flow in the transport circuit and / or in the hopper. These threads also have poor abrasion resistance.

EXAMPLES 27 TO 39

The granules of Examples 14 to 26 are used to make composite parts by the injection molding technique. The granules of cut glass yarns and the granulated thermoplastic material (polypropylene) are transported pneumatically to a gravimetric doser overlying an injection molding machine equipped with a single injection screw. The mixture is injected into a mold allowing the production of a 2 mm thick plate. The amount of glass represents 30% of the total weight of the plate. The plates were formed under the following conditions:

- Conditions 1: No pressure is applied on the injection screw operating at a speed of 130 rotations per minute.

- Conditions 2: a pressure of 120 bar (12 MPa) is applied to the injection screw operating at the speed of 130 rotations per minute, the speed being reduced to 80 rotations per minute at the end of the dosage, which allows slightly increase the mixing time of the materials and obtain better impregnation of the son by the thermoplastic material.

The plates thus formed are placed on a lighting device making it possible to visualize the clusters of cut yarns that are not dispersed in the thermoplastic matrix. An image processing software (Mesurim) of the plate makes it possible to calculate the percentage of the surface containing nondispersed cut glass threads (% defects).

The characteristics of the composite parts are given in Table 3. TABLE 3

Whatever the conditions of the molding, the plates obtained from the granules according to the invention have a better dispersion of the glass threads in the matrix and therefore a lower percentage of defects than with the known granules (comparative examples 38 and 39). ).

The molding performed under conditions 2 leads to better dispersion without significantly affecting the length of the fibers and therefore the level of performance in terms of reinforcement.

The mechanical properties of the plates reinforced by the glass strands coated with the size according to the invention are comparable to those of Examples 38 and 39, in particular the impact resistance (Charpy and IZOD tests) and the bending stress.

Claims

1. Sizing composition for glass son characterized in that it comprises the following constituents, in the following weight contents expressed as percentages of solids: - 10 to 99% of at least one copolymer chosen from copolymers of ethylene and vinyl acetate or acrylic or methacrylic acid - 1 to 40% of at least one coupling agent

- 0 to 90% polypropylene grafted with at least one unit derived from at least one monomer containing one or more functions that can react with the coupling agent.

2. Composition according to claim 1, characterized in that the copolymer has an ethylene content of at least 50% by weight, preferably at least 65% and preferably at least 80%.

3. Composition according to claim 1 or 2, characterized in that the copolymer has a melting point of less than 160 ° C, preferably less than 140 ° C and preferably of the order of 1 10 ° C.

4. Composition according to one of claims 1 to 3, characterized in that the coupling agent is chosen from silanes such as gamma-glycidoxypropyltrimethoxysilane, gamma-acryloxypropyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma-aminopropyltriethoxysilane. vinyltrimethoxysilane, phenylaminopropyltrimethoxysilane, styrylaminoethylaminopropyltrimethoxysilane or terbutylcarbanoylpropyltrimethoxysilane, siloxanes, titanates, zirconates and mixtures of these compounds.

5. Composition according to claim 4, characterized in that the coupling agent is a silane, preferably an aminosilane.

6. Composition according to one of claims 1 to 5, characterized in that the grafted polypropylene contains at least one unit derived from at least one monomer selected from vinyl monomers and monomers bearing at least one alcohol function, carboxylic acid, acid anhydride, amide or epoxide.

7. Composition according to claim 6, characterized in that the grafted polypropylene has a degree of grafting between 0.2 and 8%, preferably 0.5 and 5%.

8. Composition according to one of claims 1 to 7, characterized in that the polypropylene has melting point higher than the melting point of the copolymer.

9. Composition according to one of claims 1 to 8, characterized in that it comprises:

- 40 to 90% of at least one copolymer of ethylene and vinyl acetate or of acrylic or methacrylic acid

5 to 20% of at least one coupling agent, preferably a silane

- 10 to 60% grafted polypropylene, preferably with maleic anhydride.

10. Composition according to claim 9, characterized in that the grafted polypropylene has a degree of grafting maleic anhydride ranging from 0.2 to 6%, preferably from 0.5 to 4%.

11. Composition according to one of claims 1 to 10, characterized in that the composition further comprises at least one film-forming agent chosen from polyurethanes, epoxies, polyesters and polyvinyl acetate.

12. Composition according to claim 1 1, characterized in that the content of film-forming agent does not exceed 40% by weight of the sizing composition, preferably 10%.

13. Composition according to one of claims 1 to 12, characterized in that it has a solids content of between 2 and 20

%, preferably 4 and 15% and advantageously of the order of 10%.

14. Glass thread coated with a sizing composition according to one of claims 1 to 13.

15. Glass strand according to claim 14, characterized in that it consists of 100 to 10,000 filaments, preferably 200 to 5,000, and preferably of the order of 1,000.

16. The glass yarn according to claim 14 or 15, characterized in that it is coated with a sizing amount not exceeding 2% of the weight of the yarn and of preferably between 0.2 and 1.8%, and advantageously between 0.5 and 1.5%.

17. Granulated cut glass son, characterized in that it consists of glass son according to one of claims 14 to 16.

18. Granule according to claim 17, characterized in that it contains

95% to 99.8% by weight of glass, preferably 98 to 99.5%.

19. Granule according to claim 17 or 18, characterized in that it has a loss on ignition of less than 2% by weight, preferably less than 1.8%, and advantageously varying from 0.5 to 1.5%.

20. Granule according to one of claims 17 to 19, characterized in that it has a length of 6 to 30 mm, preferably 8 to 25 mm, and preferably 9 to 15 mm.

21. Granule according to one of claims 17 to 20, characterized in that it has a diameter of between 0.5 and 4 mm, preferably 1 to 3 mm.

22. Use of the granules according to one of claims 17 to 21 for obtaining composite parts comprising cut glass son and a thermoplastic material by the injection molding technique.

23. Use according to claim 22, characterized in that the thermoplastic material is chosen from polyolefins, polyamides, polyalkylene terephthalates, styrenic polymers, polycarbonates and polyacetals.

24. Use according to claim 23, characterized in that the thermoplastic material is polypropylene.