Composite comprising a plastisol matrix and an adhesion promoter

Abstract

The invention relates to a composite based on at least one textile reinforcing element embedded in a matrix based on polyvinyl chloride, a plasticizer, a heat stabilizer and a phenol-aldehyde resin based on: at least one aromatic polyphenol comprising at least one trivalent aromatic ring bearing at least one hydroxyl function and a group comprising a function chosen from a hydroxyl function and a methoxy function, and at least one curing agent.

Description

[0001] COMPOSITE COMPRISING A PLASTISOL MATRIX AND AN ADHESION PROMOTER

[0002] Technical field of the invention

[0003] The present invention relates to the field of composites based on a plastisol and a textile element as well as to products comprising such composites.

[0004] Prior art

[0005] Plastisols are pastes obtained from a colloidal dispersion of a powdered resin in a liquid plasticizer. These pastes are gelled by baking and used in many applications such as fabric coating, the manufacture of hollow bodies, or the coating of metal surfaces. The adhesion of the plastisol to its support, particularly textile supports, is an important characteristic for the lifespan of the articles that use it.

[0006] Several adhesion promoters have been proposed to improve the adhesion of a PVC (polyvinyl chloride) plastisol-based matrix to textile elements.

[0007] Document FR 2 304464 describes a reinforcing strip comprising a multiplicity of parallel textile filaments embedded in a polyvinyl chloride plastisol comprising a binder intended to improve adhesion to the filaments by forming a condensation resin containing formaldehyde, in particular the combination of resorcinol and hexamethylenetetramine (HMT).

[0008] Document US 4,623,686 describes a PVC plastisol comprising polyisocyanates with the aim of limiting the increase in viscosity while ensuring correct adhesion to textile elements such as polyamides or polyesters. Document WO2016 / 137738 proposes using a mixture of an isocyanurate and an organophosphate.

[0009] Another solution to improve the adhesion of textile elements to a matrix based on a PVC plastisol consists of using a bonding layer, for example an adhesive applied to one or more contact surfaces, and numerous adhesive formulations have been proposed. However, this solution involves additional steps of brushing the surface(s), as well as taking into account the specific dynamics of crosslinking of adhesives and gelation of the plastisol. Continuing its research, the applicant discovered that a resin based on a specific methylene acceptor and a hardener made it possible to improve adhesion performance, without impacting the stability of the plastisol, thus allowing easier processing of the latter to form composites, and promoting the reduction of known Health, Safety and Environment issues on the raw materials constituting the resin.The composite of the invention, which allows the use of bio-sourced compounds, helps to reduce pressure on fossil resources.

[0010] Detailed description of the invention

[0011] The invention relates to a composite based on at least one textile reinforcing element embedded in a matrix based on polyvinyl chloride (PVC), a plasticizer, a thermal stabilizer and a phenol-aldehyde resin based on ■ at least one aromatic polyphenol comprising at least one trivalent aromatic nucleus carrying at least one hydroxyl function and a group comprising a function chosen from a hydroxyl function and a methoxy function, and at least one hardening agent.

[0012] Definitions

[0013] In this document, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0014] The expression "composition based on" means a composition comprising the mixture and / or the in situ reaction product of the different constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacture of the composition; the composition can thus be in a totally or partially gelled state or in a non-gelled state.

[0015] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the range of values ​​from more than a to less than b (i.e., excluding the limits a and b), while any interval of values ​​designated by the expression "from a to b" means the range of values ​​from a to b (i.e., including the strict limits a and b). In this document, when an interval of values ​​is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also and preferably designated.

[0016] The carbon-containing compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass.

[0017] This includes polymers, plasticizers, fillers, etc.

[0018] PVC matrix

[0019] The composite according to the invention is based on a matrix based on polyvinyl chloride, a plasticizer, a thermal stabilizer and a phenol-aldehyde resin.

[0020] The matrix based on PVC and a plasticizer is known to those skilled in the art under the name “plastisol”, which is a paste obtained by colloidal dispersion of a powdery synthetic resin, in this case a PVC powder, in a liquid plasticizer.

[0021] The main role of the plasticizer is to improve the flexibility and impact and cold resistance of PVC by reducing the interactions between the polymer chains and lowering the glass transition temperature (Tg). The latter, which is between 75 and 85°C for rigid PVC, can reach -40°C for flexible PVC. The addition of plasticizer, which can represent up to 50% of the final mass of the material, improves its elongation at break.

[0022] This type of plasticization is therefore often favored by manufacturers. Thus, during external plasticization, the plasticizer is inserted between the polymer chains and acts as a "solvent". The plasticizer and the polymer are then linked by Van der Waals-type electrostatic interactions. These interactions take place between the chlorine atoms in the PVC and the electrophilic groups in the plasticizers, and their intensity depends in particular on the polarity of the plasticizer.

[0023] The plasticizer may be any plasticizer commonly used in the field of plastisols and is preferably chosen from phthalates, aliphatic dicarboxylic acid esters, epoxides and phosphates.

[0024] The polyvinyl chloride-based matrix of the composite according to the invention also comprises a thermal stabilizer.

[0025] The role of thermal stabilizers is to fix the hydrogen chlorides released during dehydrochlorination, an autocatalytic reaction due to heat, light and oxygen. Thus, stabilizers make it possible to avoid side reactions during the processing of PVC, but also to increase its thermal stability. The thermal stabilizer can be any thermal stabilizer commonly used in the field of plastisols, and is preferably chosen from lead-based stabilizers, tin-based stabilizers or calcium / zinc or calcium / organic stabilizer mixtures, preferably from tin-based stabilizers or calcium / zinc or calcium / organic stabilizer mixtures.

[0026] Aromatic polyphenol

[0027] The PVC-based matrix of the composite according to the invention comprises a phenol-aldehyde resin based on at least one aromatic polyphenol comprising at least one trivalent aromatic nucleus carrying at least one hydroxyl function and a group comprising a function chosen from a hydroxyl function and a methoxy function, and a hardening agent.

[0028] The expression "phenol-aldehyde resin based on" should of course be understood to mean a resin comprising the mixture and / or the product of the reaction between the different basic constituents used for the final condensation of this resin, preferably only the product of the reaction between the different basic constituents used for this resin, some of which may be intended to react or capable of reacting with each other or with their close chemical environment, at least in part, during the different phases of the manufacturing process of the composition, composites or an article comprising this composition or these composites, in particular during a curing step. Thus, the basic constituents are the reactants intended to react together during the final condensation of the resin and are not reactants intended to react together to form these basic constituents.

[0029] In a preferred arrangement, the aromatic polyphenol is a lignin compound.

[0030] In another preferred arrangement, the aromatic polyphenol carries three hydroxyl functions in meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted. In this preferred arrangement, the aromatic polyphenol is preferably phloroglucinol.

[0031] Hardener

[0032] The PVC-based matrix of the composite according to the invention comprises a phenol-aldehyde resin based on at least one aromatic polyphenol and a hardening agent. Preferably, the content of hardening agent in the PVC-based matrix ranges from 0.5 to 15% relative to the weight of PVC, preferably from 0.5 to 5% relative to the weight of PVC.

[0033] Any hardener capable of crosslinking the aromatic polyphenol compound used in the PVC matrix of the composite according to the invention may be suitable as a hardening agent. In particular, the hardening agent may be chosen from aldehyde compounds.

[0034] Preferably, the curing agent is an aldehyde compound, for example a compound such as 5 _ (hydroxymethyl)furfural, or an aromatic dialdehyde compound. Such an aldehyde compound is very advantageous because it avoids the production of formaldehyde, unlike conventional methylene donors. An aromatic dialdehyde is a compound comprising at least one aromatic ring, this aromatic ring carrying at least two aldehyde functions.

[0035] In a preferred arrangement, the aromatic dialdehyde compound is an aldehyde of formula A: in which X comprises N, S or O and R represents — CHO.

[0036] According to a preferred embodiment, X represents O. The aromatic dialdehyde compound then has the formula Bb :

[0037] In this embodiment, the aromatic dialdehyde compound is preferably 2,5 _ furanedicarboxaldehyde.

[0038] In another preferred embodiment, X comprises N. In a variant of this embodiment, X represents NH. The aromatic dialdehyde compound then has the formula Ca :

[0039] Preferably, in this variant, the aromatic dialdehyde compound is 2,5-1H-pyrroledicarboxaldehyde.

[0040] In another variant of this embodiment, X represents NR1 with RI representing a radical chosen from the group consisting of alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl radicals. The aromatic dialdehyde compound is then of formula (I) :

[0041] In another preferred embodiment, X comprises S. In a variant of this embodiment, X represents S and the aromatic dialdehyde compound is then of formula l )a :

[0042] Preferably, in this variant, the aromatic dialdehyde compound is 2,5-thiophenedicarboxaldehyde.

[0043] In another variant of this embodiment, X represents SR2 with R2 representing a radical chosen from the group consisting of alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl radicals. The aromatic dialdehyde compound then has the formula Db : In another variant of this embodiment, X represents R3-S-R2 with R2, R3 each independently of the other representing a radical chosen from the group consisting of alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl radicals. The aromatic dialdehyde compound then has the formula De ■

[0044] In another variant of this embodiment, X represents S=O. The aromatic dialdehyde compound then has the formula Dd :

[0045] In another variant of this embodiment, X represents O=S=O. The aromatic dialdehyde compound then has the formula De :

[0046] Among the different embodiments described above, the embodiments and variants in which X represents NH, S or O will be preferred. In these embodiments and variants, R, which represents the -CHO group, will preferably be in position 5 and the —CHO group in position 2 on the aromatic ring.

[0047] Preferably, the two meta positions of at least one aldehyde function of the curing agent are unsubstituted.

[0048] Very preferably, the aromatic aldehyde is chosen from the group consisting of 1,4-benzene-dicarboxaldehyde, 1,3-benzene-dicarboxaldehyde, 2,5-furanedicarboxaldehyde and mixtures of these compounds, and very preferably 1,4-benzene-dicarboxaldehyde. Preferably, the curing agent is chosen from a carbamide, 5-(hydroxymethyl)furfural, 1,4-benzene-dicarboxaldehyde and 1,3'benzene'dicarboxaldehyde, preferentially chosen from 1,4-benzene-dicarboxaldehyde and 1,3-benzene-dicarboxaldehyde.

[0049] Additives

[0050] The PVC-based matrix of the composite according to the invention may also include all or part of the usual additives and processing agents, known to those skilled in the art and usually used in plastisol compositions, such as, for example, pigments or protective agents.

[0051] Preferably, the PVC-based matrix of the composite according to the invention does not comprise isocyanate compounds or comprises less than 5% by weight relative to the weight of PVC, preferably less than 2% by weight, preferably less than 1% by weight and very preferably less than 0.5% by weight.

[0052] Reinforcing element

[0053] The composite according to the invention comprises at least one textile reinforcing element. A textile reinforcing element is made of an organic material, in particular polymeric, or inorganic, such as for example glass, quartz, basalt or carbon.

[0054] The textile reinforcing element may be wire-like, i.e. have a length at least 10 times greater than the largest dimension of its section, whatever the shape of the latter: circular, elliptical, oblong, polygonal, in particular rectangular, square or oval. In the case of a rectangular section, the textile reinforcing element has the shape of a strip.

[0055] The textile reinforcing element may also be in the form of a film, that is to say that it extends in two main directions and has a very low thickness compared to each of its other main dimensions, at least 100 times less, preferably at least 1000 times less.

[0056] The textile reinforcing element may be a textile elementary monofilament. This textile elementary monofilament is obtained, for example, by melt spinning, solution spinning or gel spinning. Each textile elementary monofilament is made of an organic material, in particular polymeric, or inorganic, such as for example glass, quartz, basalt or carbon. The polymeric materials may be of the thermoplastic type, such as for example aliphatic polyamides, in particular polyamides 6-6, and polyesters, in particular polyethylene terephthalate. The polymeric materials may be of the non-thermoplastic type, such as for example aromatic polyamides, in particular aramid, and cellulose, both natural and artificial, in particular rayon. Each textile elementary monofilament preferably has a substantially circular section with a diameter ranging for example from 2 μm to 100 μm.

[0057] The textile reinforcing element may be an assembly of several elementary textile monofilaments as defined above, also called strand. A strand preferably comprises more than 10 elementary textile monofilaments, preferably more than 100 elementary textile monofilaments and more preferably more than 500 elementary textile monofilaments.

[0058] The textile reinforcing element may also be an assembly of several strands as defined above.

[0059] The textile reinforcing element is preferably of the polyester type, advantageously of the polyethylene terephthalate, polyamide, glass, carbon, quartz or basalt type.

[0060] According to a preferred embodiment, the composite according to the invention comprises a multiplicity of reinforcing elements as defined above arranged side by side in a main direction.

[0061] According to another preferred embodiment, the composite comprises several fibers assembled in a knit or fabric.

[0062] Knitting means an assembly of textile reinforcing elements as defined above and comprising stitches formed by one or more of these textile reinforcing elements. Each stitch comprises a loop interlaced with another loop. Examples include jersey or English rib knits for weft knits and charmeuse or atlas knits for warp knits.

[0063] By fabric is meant an assembly of textile reinforcing elements either in an ordered manner, in which a first family of reinforcing elements, called warp elements, substantially parallel to each other and extending in a first main direction, and a second family of reinforcing elements, called weft elements, substantially parallel to each other and extending in a second main direction are assembled together, the warp elements passing successively above and below the weft elements according to a pattern defining the weave of the fabric, or in a disorderly or random manner, so as to form a non-woven fabric.

[0064] In a preferred embodiment, which can be associated with any reinforcement element configuration described previously, the reinforcement element is made up of at least two different materials (so-called “hybrid” element) chosen from an organic material, in particular polymeric, or inorganic, such as for example glass, quartz, basalt or carbon.

[0065] Reinforced product

[0066] The invention also relates to a reinforced product comprising at least one composite according to the invention or a semi-finished article according to the invention.

[0067] The reinforced product is preferably a product comprising at least one composite according to the invention embedded in a rubber composition matrix.

[0068] Said rubber composition matrix is ​​based on at least one elastomer, diene or non-diene (for example thermoplastic). It is preferably a composition of the crosslinked or crosslinkable type, that is to say that it then comprises a crosslinking system, in particular a vulcanization system, adapted to allow the crosslinking of the composition during its curing, or the curing of the finished product in which the composite is incorporated.

[0069] Such a reinforced product may be chosen in particular, and in a non-limiting manner, from conveyor belts, transmission belts, tracks, tires for pneumatic or non-pneumatic wheels.

[0070] A pneumatic tire is a wheel tire made capable of supporting a load by being pressurized by a gas, usually air. A non-pneumatic tire is a wheel tire capable of supporting a load by a means other than being pressurized, for example by means of stays.

[0071] Manufacturing process

[0072] The invention also relates to a method for manufacturing a composite according to the invention comprising at least the steps of ■

[0073] Mixture of the aromatic polyphenol with a portion of the plasticizer sufficient to solubilize said aromatic polyphenol at a temperature between 100°C and 150°C Mixture of the polyvinyl chloride powder with a fraction of the plasticizer so as to obtain a homogeneous paste

[0074] Addition of the heat stabilizer and the remainder of the plasticizer to the polyvinyl chloride paste; Incorporation of the solubilized aromatic polyphenol into the polyvinyl chloride paste at room temperature;

[0075] Incorporation of the curing agent into the polyvinyl chloride paste at room temperature.

[0076] Examples

[0077] Preparation of the compositions

[0078] Each composition presented in Table 1 is prepared by mixing the components at low speed, in a blender equipped with a kneader, at room temperature until a homogeneous paste is obtained.

[0079] The PVC powder is first introduced into the blender, then a small amount of liquid plasticizer is mixed into the powder until a homogeneous paste is obtained. Finally, the remaining plasticizer and the heat stabilizer are introduced.

[0080] Part of the plasticizer is used to solubilize the resorcinol or phloroglucinol at 130°C, before introduction into the plastisol mixture described above. The hardening agent is introduced last into the composition.

[0081] The plastisol mixture is then stored in an airtight container at room temperature for 24 hours before preparing the test specimens.

[0082] Viscosity measurement

[0083] After preparing the different compositions, the viscosity is measured immediately after preparation (viscosity “at 0 days”) and after 14 days.

[0084] Viscosity is measured using a Brookfield / Mobil N°62 / LV'02 viscometer using the following protocol: ■ the sample is transferred into the thermostatically controlled chamber up to approximately 150 mL (inner beaker graduation) while avoiding the formation of air bubbles. The sample is allowed to regulate at the measurement temperature of 23°C for the indicated time, i.e. 1 to 20 minutes depending on the starting temperature of the composition. In a manner known to those skilled in the art, the speed is selected, for example 10 rpm or 30 rpm, and the spindle is set to rotate. The axis is waited for to stabilize (1 minute) before taking the first reading and the result is read on the digital display (viscosity in cP). Preparation of the test pieces

[0085] A PET yarn made of 8 strands of 1100 dTex is attached on either side of a mold made of two parts, each part comprising a half-cylinder shaped cavity, and is held under low tension by a weight and screws, without altering the twist of the yarn.

[0086] The two parts of the mold are heated separately to 160°C. The tested composition is then placed in each of the semi-cylindrical cavities. The mold is left open for 5 minutes at 160°C, which allows for pre-gelation. The mold is then closed and pressed at 200kN for 20 minutes to form a cylindrical specimen, with the yarn passing through the cylinder along the cylinder axis. Once the mixture has gelled, the mold is cooled to room temperature before removing the specimens from the mold. The specimens are stored at room temperature for at least 24 hours before being tested.

[0087] Measurement of pull-out forces

[0088] To measure the pull-off force of the yarn from the composition, the PET yarn is pulled out of the cylindrical block using a tensile machine according to the method described in ASTM D 2229-02. The pulling speed is 250 mm / min. The adhesion of the composition to the reinforcement is thus characterized by the force required to pull the reinforcement out of the test piece, at a temperature of 23°C.

[0089] [Table 1]

[0090] (1) Vinnolit PVC, “P 4472”

[0091] (2) phthalate-type plasticizer, “Reofos” from Lanxess

[0092] (3) heat stabilizer for PVC, “AKCROSTAB LZB6159” from Valtris (4) dispersion of Hexamine in a chlorinated paraffin from PolyBlend UK

[0093] (5) Resorcinol (CAS No. 108-46 _ 3) from Sigma Aldrich

[0094] (6) Phloroglucinol (CAS no. 108'73'6) from Sigma Aldrich

[0095] (7) Terephthalaldehyde (CAS No. 623-27'8) from Sigma Aldrich

[0096] The compositions in accordance with the invention exhibit improved adhesion performance as well as low scalability over time.

Claims

CLAIMS Composite based on at least one textile reinforcement element embedded in a matrix based on polyvinyl chloride, noted PVC, a plasticizer, a thermal stabilizer and a phenol-aldehyde resin based on ■ • at least one aromatic polyphenol comprising at least one trivalent aromatic nucleus carrying at least one hydroxyl function and a group comprising a function chosen from a hydroxyl function and a methoxy function, and • at least one hardening agent. Composite according to claim 1 in which the hardening agent is chosen from aldehyde compounds. Composite according to the preceding claim in which the hardening agent is a dialdehyde compound comprising at least one aromatic nucleus, substituted or not. Composite according to the preceding claim in which the two meta positions of at least one aldehyde function of the hardening agent are unsubstituted. Composite according to claim 1 in which the hardening agent is chosen from a carbamide, 5-(hydroxymethyl)furfural, 1,4-benzene-dicarboxaldehyde and 1,3-benzene-dicarboxaldehyde, preferentially chosen from 1,4-benzene-dicarboxaldehyde and 1,3-benzene-dicarboxaldehyde. Composite according to any one of the preceding claims in which the content of hardening agent in the PVC-based matrix ranges from 0.5 to 15% relative to the weight of PVC, preferably from 0.5 to 5% relative to the weight of PVC.Composite according to any one of the preceding claims in which the aromatic polyphenol carries three hydroxyl functions in the meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted, and preferably the aromatic polyphenol is phloroglucinol. Composite according to any one of the preceding claims in which the textile reinforcing element comprises a material chosen from aliphatic polyamides, polyesters, aromatic polyamides, cellulose, glass, quartz, basalt or carbon and mixtures thereof. Composite according to the preceding claim in which the textile reinforcing element comprises a material chosen from aliphatic polyamides, polyesters, aromatic polyamides and cellulose and mixtures thereof. Composite according to claim 8 wherein the textile reinforcing element comprises a material selected from glass, quartz, basalt or carbon. Composite according to any one of the preceding claims comprising a multiplicity of textile reinforcing elements arranged side by side in a main direction. Composite according to any one of claims 1 to 10 comprising several fibers assembled in a knit or fabric. Reinforced product comprising at least one composite according to any one of claims 1 to 12. Reinforced product according to the preceding claim selected from conveyor belts, transmission belts, tracks, tires for pneumatic or non-pneumatic wheels. Method of manufacturing a composite according to any one of claims 1 to 12 comprising at least the steps of ■ • Mixture of the aromatic polyphenol with a portion of the plasticizer sufficient to solubilize said aromatic polyphenol at a temperature between 100°C and 150°C • Mixing the polyvinyl chloride powder with a fraction of the plasticizer to obtain a homogeneous paste; • Addition of heat stabilizer and remaining plasticizer to polyvinyl chloride paste • Incorporation of solubilized aromatic polyphenol into polyvinyl chloride paste at room temperature • Incorporation of the hardening agent into the polyvinyl chloride paste at room temperature; • Embedding of at least one textile reinforcement element.

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