FR3140629A1 - COMPOSITE COMPRISING A PLASTISOL MATRIX AND AN ADHESION PROMOTER - Google Patents

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 thermal stabilizer and a phenol-aldehyde resin based on: d at least one aromatic polyphenol comprising at least one trivalent aromatic ring 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.

Description

COMPOSITE COMPRISING A PLASTISOL MATRIX AND AN ADHESION PROMOTER Technical field of the invention

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.

Prior art

Plastisols are pastes obtained from a colloidal dispersion of a resin in powder form in a liquid plasticizer. These pastes are gelled by cooking and used in numerous applications such as the coating of fabrics, the manufacture of hollow bodies or the coating of metal surfaces. The adhesion of plastisol to its support, particularly textile supports, is an important characteristic for the lifespan of the articles using it.

Several adhesion promoters have been proposed in order to improve the adhesion of a matrix based on a PVC (polyvinyl chloride) plastisol on textile elements.

Document FR 2 304 464 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 hexamethylene tetramine (HMT).

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.

Another solution for improving 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 formulations of adhesives were proposed. However, this solution involves additional steps of painting the surface(s), as well as taking into account the specific dynamics of glue crosslinking and plastisol gelling.

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 implementation of the latter to form composites, and promoting the reduction of Hygiene, Safety and Environment issues known to the raw materials constituting the resin. The composite of the invention, which makes it possible to use biosourced compounds, helps to reduce pressure on fossil resources.

Detailed description of the invention

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 with base :

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.

Definitions

Herein, unless expressly stated otherwise, all percentages (%) shown are percentages (%) by mass.

By the expression "composition based on", is meant 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 less partially, during the different phases of manufacturing the composition; the composition can thus be in a totally or partially gelled state or in a non-gelled state.

On the other hand, any interval of values designated by the expression "between a and b" represents the range of values going from more than a to less than b (that is to say limits a and b excluded) while any interval of values designated by the expression "from a to b" means the range of values going from a to b (that is to say including the strict limits a and b). In the present document, when we designate an interval of values by the expression "from a to b", we also and preferentially designate the interval represented by the expression "between a and b".

The compounds comprising carbon mentioned in the description may be of fossil or biosourced origin. In the latter case, they can be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. This concerns in particular polymers, plasticizers, fillers, etc.

PVC matrix

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.

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.

The main role of the plasticizer is to improve the flexibility and resistance to impact and cold of PVC by reducing the interactions between the polymer chains and lowering the glass transition temperature (Tg). The latter, with a value 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, makes it possible to improve its elongation at break.

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

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

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

The role of thermal stabilizers is to fix the hydrogen chlorides released during dehydrochlorination, an auto-catalytic reaction due to heat, light and oxygen. Thus, stabilizers make it possible to avoid secondary reactions when using 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 stabilizers based on lead, stabilizers based on tin or calcium/zinc or calcium/organic stabilizers mixtures, preferably among stabilizers based on tin or calcium/zinc or calcium/organic stabilizers mixtures.

Aromatic polyphenol

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.

By the expression “phenol-aldehyde resin based on”, we must of course understand 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 them being 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 process manufacturing the composition, composites or an article comprising this composition or these composites, in particular during a cooking step. Thus the basic constituents are the reagents intended to react together during the final condensation of the resin and are not reagents intended to react together to form these basic constituents.

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

In another preferred arrangement, 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. In this preferred arrangement, the aromatic polyphenol is preferably phloroglucinol.

Hardener

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.

As a hardening agent, any hardener capable of crosslinking the aromatic polyphenol compound used in the PVC matrix of the composite according to the invention may be suitable. In particular, the hardening agent can be chosen from aldehyde compounds.

Preferably, the hardening 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 nucleus, this aromatic nucleus carrying at least two aldehyde functions.

In a preferred arrangement, the aromatic dialdehyde compound is an aldehyde of formula A:
(HAS)

in which X includes N, S or O and R represents –CHO.

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

In this embodiment, the aromatic dialdehyde compound is preferably 2,5-furanedicarboxaldehyde.

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:
(That)

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

In another variant of this embodiment, The aromatic dialdehyde compound then has the formula Cb:
(Cb)

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 Da:
(Da)

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

In another variant of this embodiment, The aromatic dialdehyde compound then has the formula Db:
(Db)

In another variant of this embodiment, The aromatic dialdehyde compound then has the formula Dc:
(DC)

In another variation of this embodiment, X represents S=O. The aromatic dialdehyde compound then has the formula Dd:
(Dd)

In another variation of this embodiment, X represents O=S=O. The aromatic dialdehyde compound then has the formula De:
(Of)

Among the different embodiments described above, we will prefer the embodiments and variants in which X represents NH, S or O. In these embodiments and variants, we will preferentially have R, which represents the group -CHO, in position 5 and the –CHO group in position 2 on the aromatic ring.

Preferably, the two meta positions of at least one aldehyde function of the hardening agent are unsubstituted.

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 hardening agent is chosen from a carbamide, 5-(hydroxymethyl)furfural, 1,4-benzene-dicarboxaldehyde and 1,3-benzene-dicarboxaldehyde, preferably chosen from 1,4-benzene- dicarboxaldehyde and 1,3-benzene-dicarboxaldehyde.

Additives

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.

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.

Reinforcement element

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

The textile reinforcing element can be wire, that is to say 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 or square or oval. In the case of a rectangular section, the textile reinforcing element has the shape of a strip.

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

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

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.

The textile reinforcing element can also be an assembly of several strands as defined above.

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

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.

According to another preferred embodiment, the composite comprises several fibers assembled into knitted fabric or fabrics.

By knitting, we mean an assembly of textile reinforcing elements as defined above and comprising stitches formed by one or more of these textile reinforcing elements. Each stitch includes a loop interwoven with another loop. We can mention, for example, jersey or English rib texture knits for picked-stitch knits and charmeuse or atlas texture knits for warp-stitch knits.

By fabric, we mean an assembly of textile reinforcing elements either in an ordered manner, in which a first family of reinforcing elements, called chain 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 in a pattern defining the weave of the fabric, either in a disorderly or random manner, so as to form a non-woven fabric.

In a preferred embodiment, which can be associated with any reinforcing element configuration described above, the reinforcing 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 glass, quartz, basalt or carbon.

Reinforced product

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.

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

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

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

By pneumatic tire we mean a tire for a wheel made capable of supporting a load due to its being put under pressure by a gas, generally air. By non-pneumatic tire we mean a tire for a wheel capable of supporting a load by a means other than putting it under pressure, for example by means of stays.

Manufacturing process

The invention also relates to a method of manufacturing a composite according to the invention 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;

Adding the thermal stabilizer and the rest of the plasticizer to the 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.

Examples

Preparation of compositions

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 dough is obtained.

The PVC powder is first introduced into the blender, then a small quantity of liquid plasticizer is mixed with the powder until a homogeneous paste is obtained. Finally, the rest of the plasticizer and the thermal stabilizer are introduced.

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

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

Viscosity measurement

At the end of the preparation of the different compositions, the viscosity is measured just after preparation (“0 day” viscosity) and after 14 days.

The viscosity is measured using a viscometer of the Brookfield / Mobil Viscometer type N°62 / LV-02 using the following protocol: the sample is transferred into the thermostatic chamber up to approximately 150 mL (inner beaker graduation) in avoiding the formation of air bubbles. The sample is allowed to adjust to 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, we select the speed, for example 10 rpm or 30 rpm, and we put the mobile into rotation, we wait until the axis is stabilized (1 minute) before taking the first reading and we read the result on the digital display (viscosity in cP).

Preparation of test specimens

A PET yarn made up of 8 strands of 1100 dTex is attached to either side of a mold made up of two parts, each part comprising a cavity in the shape of a half-cylinder, and is held under low tension thanks to a weight and screws, without altering the twist of the yarn.

The two parts of the mold are heated separately to 160°C. The tested composition is then deposited in each of the half-cylindrical cavities. The mold is left open for 5 min at 160°C, which allows pre-gelling. The mold is then closed and pressed at 200kN for 20 minutes to form a cylindrical test piece, the yarn passing through the cylinder along the axis of the latter. Once the mixture has gelled, the mold is cooled to room temperature before removing the test pieces from the mold. The test pieces are stored at room temperature for at least 24 hours before being tested.

Measurement of pull-out forces

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

(1) Vinnolit PVC, “P 4472”

(2) phthalate type plasticizer, “Reofos” from the company Lanxess

(3) thermal stabilizer for PVC, “AKCROSTAB LZB6159” from the company Valtris

(4) dispersion of Hexamine in chlorinated paraffin from the company PolyBlend UK

(5) Resorcinol (CAS n°108-46-3) from Sigma Aldrich

(6) Phloroglucinol (CAS n°108-73-6) from Sigma Aldrich

(7) Terephthalaldehyde (CAS n°623-27-8) from Sigma Aldrich

The compositions in accordance with the invention have improved adhesion performance as well as low scalability over time.

Claims (15)

Composite based on at least one textile reinforcing element embedded in a matrix based on polyvinyl chloride, denoted 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
• of 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 ring, 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, preferably 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 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 their mixtures . 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 their mixtures. Composite according to claim 8 in which the textile reinforcing element comprises a material chosen 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 knitted 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 chosen from conveyor belts, transmission belts, tracks, tires for pneumatic or non-pneumatic wheels. Process for 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;
• Adding the thermal stabilizer and the rest of the plasticizer to the 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 reinforcing element.