FR2908777A1 - USE OF COMPOSITION BASED ON POLYOLEFINS FOR PREPARING RETICULATED SOFT FOAMS. - Google Patents

Abstract

The present invention relates to the use in the field of automobiles, transport vehicles, the building of a composition for obtaining a crosslinked foam, said composition comprising (A) a copolymer of ethylene and an unsaturated monomer bearing at least one epoxide group and optionally alkyl (meth) acrylate or vinyl carboxylate, (B) a copolymer of ethylene and an alkyl (meth) acrylate or vinyl carboxylate (C) a polymerization initiator; and (D) a porogen.

Description

USE OF COMPOSITION BASED ON POLYOLEFINS FOR PREPARING

  RETICULATED SOFT FOAMS. Field of the invention The present invention relates to the use of polyolefin-based compositions for obtaining flexible reticulated foams and their uses in the field of automobiles, transport vehicles and buildings for their improved mechanical properties. Technological Background of the Invention Flexible foams are mainly used for the soundproofing of vehicles, in this field, patent application FR 2783831 describes flexible foams obtained from compositions comprising copolymers chosen from the group of ethylene / acetate copolymers. vinyl, ethylene / propylene / diene monomer terpolymers, butyl rubber based on polyolefin copolymers.

There is a need for a new type of flexible foam as an alternative to existing systems. Summary of the invention. The object of the present invention is therefore to provide compositions useful for the preparation of flexible foams. These flexible foams find their applications in the field of the automobile, transport vehicles, building. Thus, the invention proposes the use of a composition for obtaining a crosslinked foam, said composition comprising: (A) a copolymer of ethylene and an unsaturated monomer bearing at least one epoxide group and optionally alkyl (meth) acrylate or vinyl carboxylate; (B) a copolymer of ethylene and alkyl (meth) acrylate or vinyl carboxylate; (C) a polymerization initiator and; (D) a pore-forming agent. 3o. Preferably, the unsaturated epoxide of the copolymer (A) is glycidyl (meth) acrylate and the alkyl (meth) acrylate of the copolymer (A) is chosen from methyl (meth) acrylate, acrylate and (meth) acrylate. ethyl, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate. Preferably, the (meth) acrylate of the copolymer (B) is chosen from methyl (meth) acrylate, ethyl acrylate, n-butyl acrylate and isobutyl acrylate. 2-ethylhexyl acrylate.

Preferably, the polymerization initiator (C) is an initiator of ionic type, preferably of cationic type. Preferably, the composition further comprises at least one compound (E) of the plasticizer type E 1 or plasticizer E 2. Preferably, the plasticizer E 1 is chosen from phthalates, adipates and alkyl benzoates, the alkyl chain comprising a carbon number greater than 6. Preferably, the plasticizer E 2 is chosen from aliphatic or naphthenic oils. According to one embodiment, the content by weight of the compound (B) relative to the total weight of the composition represents at least 10%, preferably in the range of 25% to 75% by weight, or Preferably, in the range of 30 to 60%, according to one embodiment, the weight content of the polymerization catalyst (C) relative to the total weight of the composition is from 0.01% to 5%, preferably in the range from 0.1% to 2% by weight According to one embodiment, the content by weight of the compound (E) relative to the total weight of the composition represents from 0.5% to 15% by weight, preferably in the range of 2% to 10% by weight, preferably in the range of 2 to 6%.

According to one embodiment, the composition further comprises other additives selected from mineral fillers, reinforcements, flame retardants and dyes. Preferably, a flexible foam according to the invention is used as sound insulating element, seal and / or automotive door seal.

Figures. FIG. 1 illustrates the evolution of the mechanical properties of the crosslinked compositions according to the invention as a function of the Lotryl content provided in table 1. FIG. 2 illustrates the comparison of the times necessary to reach 90% of the maximum module level t90% for a Lotader -Lotryl 70-30 mixture at different levels of epoxidized soybean oil and at different temperatures, provided in Table 2. Detailed description of the embodiments of the invention. The compositions for preparing the flexible foams according to the invention comprise: (A) a first copolymer of ethylene and an unsaturated monomer (i) bearing at least one epoxide group and (ii) optionally (meth) alkyl acrylate or vinyl carboxylate; (B) a second copolymer of ethylene and an alkyl (meth) acrylate or vinyl carboxylate; (C) a polymerization initiator and; (D) a pore-forming agent. (i) the unsaturated monomer comprising at least one epoxide group is a monomeric unit derived from a compound containing at least one epoxy group and copolymerizable with ethylene. By way of example of unsaturated epoxides (i), mention may be made of: aliphatic glycidyl esters and ethers such as allyl glycidyl ether, vinyl glycidyl ether, glycidyl maleate and itaconate, and (meth) acrylate glycidyl, and alicyclic glycidyl esters and ethers such as 2-cyclohexene-1-glycidyl ether, cyclohexene-4,5-diglycidyl carboxylate, cyclohexene-4-glycidyl carboxylate, 5-norbornene-2-methyl -2-glycidyl carboxylate and endo cis-bicyclo (2,2,1) -5-heptene-2,3-diglycidyl dicarboxylate. The copolymer of ethylene and unsaturated epoxide may also comprise other monomers (ii) comprising an unsaturated ester group and which may be chosen, for example, from: - vinyl esters of saturated carboxylic acids, such as vinyl, vinyl propionate or vinyl butyrate; saturated carboxylic acid esters such as alkyl (meth) acrylates having up to 24 carbons. Preferably, the copolymer (A) according to the invention is a copolymer of ethylene and an unsaturated epoxide which can be obtained by copolymerization of ethylene and an unsaturated epoxide or by grafting the unsaturated epoxide. on polyethylene. The grafting may be carried out in the solvent phase or on the molten polyethylene in the presence of a peroxide. These grafting techniques are known per se. As for the copolymerization of ethylene and an unsaturated epoxide, it is possible to use the so-called radical polymerization processes, usually operating at pressures between 200 and 2500 bar. By way of example, the unsaturated epoxide can be grafted onto the following polymers: polyethylene, copolymers of ethylene and of an alphaolefin, polyethylenes such as VLDPE (very low density PE), ULDPE (PE ultra low density) or metallocene PE; Copolymers of ethylene and at least one vinyl ester of saturated carboxylic acid such as vinyl acetate, vinyl propionate or vinyl butyrate. Copolymers of ethylene and at least one unsaturated carboxylic acid ester, such as alkyl (meth) acrylates having up to 24 carbons; EPR elastomers (ethylene / propylene rubber) or EPDM (ethylene / propylene / diene); s - mixtures of polymers chosen from the preceding ones. The copolymer (A) of the invention is advantageously an ethylene / alkyl (meth) acrylate / unsaturated epoxide copolymer. Advantageously, it may contain up to 40% by weight of alkyl (meth) acrylate. The amount of alkyl (meth) acrylate is advantageously 20 to 35%, unsaturated epoxide is advantageously glycidyl (meth) acrylate, Advantageously, the (meth) acrylate is chosen from ( Methyl (meth) acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate.

This copolymer can be obtained by radical polymerization of the monomers. (B) the second copolymer comprises a copolymer of ethylene and an alkyl (meth) acrylate or vinyl carboxylate. The alkyl (meth) acrylate and vinyl carboxylate may be chosen from those mentioned above in the description of (A).

This second polymer does not comprise epoxy type monomer units (ii). This compound acts as a non-reactive diluent in the unfoamed composition. Due to its presence, the mechanical properties of non-foamed crosslinked materials are improved. In a preferred embodiment, the weight content of the compound (B) relative to the total weight of the composition is at least 10%, preferably in the range of 25% to 75% by weight. (C) the polymerization initiator or initiator. All polymerization initiators are capable of being used according to the invention, according to all the embodiments well known in the prior art. However, to avoid the use of compounds that generate VOCs, it is preferred not to use peroxide initiators. Thus, among the preferred polymerization initiators, mention may be made of all the initiators of ionic type such as those described in application US 2003/0176585 in paragraphs [0039] to [0049].

In addition, the agents preferably used in the present invention are the initiators of cationic type and in particular the BF3 complexes in solid or liquid form, such as the BFs-monoethylamine, BF3-benzylamine and BFsmonoisopropylamine complexes. For reasons of ease of use in polymer blending operations, the solid forms of BF3 complexes are preferred. s A combination of different initiators may be considered. The weight content of the polymerization catalyst (C) relative to the total weight of the composition is from 0.01% to 5%, preferably in the range of 0.1% to 2% by weight. (D) the blowing agent or extension agent. The blowing agents are divided into two main classes: volatile organic compounds such as chlorofluorocarbons (CFCs) and chemical agents such as azodicarbonamide All blowing agents may be used in accordance with according to all well-known embodiments of the prior art, however, to avoid the use of VOC-generating compounds, it is preferred to use alone or in admixture the blowing agents selected from azodicarbonamide, or oxybis (benzene sulfonyl hydrazide (OBSH), para-toluenesulphonyl hydrazide, expancel sold by AkzoNobel The weight content of the compound (D) relative to the total weight of the composition is at most 5% ( E) The plasticizer or plasticizer compound A plasticizer or plasticizer compound (E) may be added in the compositions according to the invention As a plasticizer, this compound (E1) is chosen from aliphatic or naphtha oils. As a plasticizer, this compound (E2) is chosen from phthalates (for example di-octyl phthalate), adipates (for example di (2-ethylhexyl) adipate) and alkyl benzoates, the alkyl chain comprising a carbon number greater than 6. These compounds are used in solid or fluid form. Preferably, when adding a fluidizer (E2), it can be functionalized, and is preferably used epoxidized soybean oil (Arkema Ecepox). These compounds may be used alone or as a mixture and it may especially be used a mixture containing both a plasticizer and a plasticizer. The content by weight of the compound (E) relative to the total weight of the composition represents from 0.5% to 15% by weight, preferably in the range from 2% to 10% by weight.

The addition of this compound in the unfoamed composition accelerates the crosslinking reaction and thus counterbalances the decrease in the crosslinking rate due to the presence of the compound (B). (F) other additives or fillers It is not beyond the scope of the invention by adding mineral fillers (talc, CaCO3, kaolin ...), reinforcements (glass fibers, mineral fibers, carbon fibers, etc.). ..), flame retardants and dyes. s Process for the preparation of crosslinked flexible foams 1) Mixing step of the ingredients and obtaining a non-crosslinked composition: Several methods of preparation can be used. The most common is to dry mix all components: polymers (A) and (B), porogen (D) and initiator (C). The mixtures of the compounds are made in an internal mixer (Brabender type). The ingredients are introduced into the preheated mixer at a temperature chosen so as to be just above the melting temperature of the polymers. Once the polymers are melted, optionally the compound (E) is added. Once the mixture has become homogeneous, the polymerization initiator (C) is added. The mixing time is generally 5 to 10 min from the end of addition of the initiator. Another way to prepare the mixture is to extrude the mixture (A) and (B) to obtain a homogeneous mixture. This mixture is then taken up in the internal mixer as previously described. Other types of mixer can be used as single-screw extruders, twin-screw, BUSS co-kneader. Another way of preparing the mixture is to carry out a premixing of the polymers and to add, in a second step, the pore-forming agent and then the initiator.

Another possibility is to make the mixture (A) and (B) entirely extrusion with injection of the compound (E) if it is liquid. Here the technical difficulty is to avoid the initiation of the crosslinking reaction during this transformation step, the self heating in extruder being larger than in kneader. According to another embodiment, rather of industrial type, the compositions 30 may be prepared in an internal mixer or extruder and then granulated. In the case of an addition of liquid plasticizer or fluidizer for example of the epoxidized soybean oil type, it can be added to the dry mix to impregnate the granules if its amount is small. If the quantity is large, the liquid will be injected. Non-foamed uncrosslinked blends, for example in the form of granules, can then be shaped by injection or compression at low temperature, to form a preformed structure or a plate. During this step, it should avoid crosslinking or foaming the room. For this purpose, the transformation must be carried out at a low temperature, for example between 20 ° C. and 100 ° C., and in a short time, for example between 10 and 60 min. The preformed structure may advantageously then be positioned in the structure of a vehicle before the crosslinking and foaming step, for example by heating when passing through a heating tunnel. If provision is made for the presence of other additives, these would be introduced during the mixing step (internal mixer or extrusion), just before the initiator which is always introduced last. 2) Crosslinking and foaming step. The crosslinking step is carried out by any type of crosslinking process according to the type of initiator used and according to methods well known in the art. Preferably, with the initiators of cationic type and more particularly the complexes of BF3, the crosslinking is carried out by heating. Heating is usually done in an oven. The oven is preheated to a temperature ranging from 150 C to 200 C and preferably 175 C. This is the average temperature of the heating tunnels used in the automotive industry. The residence time in the heating tunnel is estimated at 30 min. During heating, the expansion of the crosslinked polyolefin foams occurs in all three dimensions, when no particular stress is applied.

It is important to carefully control the degree of crosslinking of the resin at the beginning of the expansion and throughout its duration; the content of the starting compositions of expansion agent and crosslinking in the case of chemical crosslinking is, of course, adapted for this purpose as well as the times and temperatures of the heat treatments. In the preparation of crosslinked polyolefin foam, the onset of expansion usually takes place in an already partially crosslinked state of the composition. This measure aims to increase the viscosity of the composition and thus conditions the regularity and fineness of the cell structure finally obtained. In this case, the crosslinking continues during the expansion and, optionally, after. Soft foams. 3o The foams obtained according to the process described above have a compression, measured according to the ASTM D 1667 standard with a compression ratio of 30 and a compression speed of 10 mm / min, at most equal to 7 N / cm 2 for a density of at least 100 kg / m3, it being understood that this maximum compression is likely to decrease for lower densities and to increase for higher densities. Preferably, the gel level of this foam, defined as the weight percentage of the insoluble fraction (in dry extract) of a sample of 50 mg immersed for 24 hours at 120 ° C. in 25 ml of dried xylene over molecular sieves. is between 30 and 70%, especially between 40 and 60%. Use of the compositions according to the invention The compositions according to the invention are used for making flexible foams which are used in the field of the automobile, transport vehicles, the building, in particular as sound insulation, gasket, automobile door seal, etc. The mechanical properties of the flexible foams obtained from the compositions according to the invention are related to the mechanical and rheological properties of the non-foamed crosslinked compositions EXAMPLES The following examples are intended to illustrate the invention without limiting its scope. In the examples which follow, the components used are as follows: The copolymer (A) is a copolymer of ethylene (67%) - methyl acrylate 14 (25%) - glycidyl methacrylate (8%) manufactured by Arkema under the reference Lotader GMA AX8900 with a Melt Flow Index (MFI) of 6g / 10min measured according to ASTM D1238 and a melting point of 60 C measured by differential scanning calorimetry The copolymer (B) is a copolymer ethylene (62%) -methyl acrylate (28%) manufactured by Arkema under the reference Lotryl 28MA07, whose MFI is 6-8 g / 10 min measured according to ASTM D1238 and the melting point is 65 C measured by differential scanning calorimetry. Compound (C) is a BF3-monoethylamine complex. The compound (D) pore-forming agent is the Genitron EPC from Lanxess.

The compound (E) is epoxidized soybean oil under the reference Ecepox PB3 (oxirane number equal to 6.5-7.5 g O 2/100 g). EXAMPLE 1 Preparation of the crosslinked compositions according to the invention 1) Mixing step of the ingredients: The mixtures are made in an internal mixer (Brabender type). The 3o lotader and lotryl polymers are introduced into the mixer preheated between 90 ° C. and 110 ° C. This temperature is chosen so as to be just above the melting point of the two polymers. Once the polymers are melted, Ecepox epoxidized soybean oil is added. Once the mixture has become homogeneous, the BF3 monoethylamine complex initiator is added. The mixing time is 5 minutes from the end of the addition of the initiator. 2) Crosslinking and foaming step: The crosslinking step is done in an oven. The oven is preheated to 175 C. The compositions from the internal mixer are previously compressed at 90 C or 110 C so as to obtain a plate. Samples are then cut and placed in the oven for 30min. It is during this step that the system reticules. EXAMPLE 2 Properties of the Products Obtained: Mechanical Properties. Experimental Technique: Modulus values, tensile strength and elongation at break were determined on IFC type tensile specimens with a thickness of 1.2 mm. The experiments are carried out on an extensometer at 50 mm / min.To characterize the crosslinking kinetics, shear modulus monitoring experiments G '(conservation modulus) and G "(loss modulus) were carried out at different isotherms (150 C, 160 C, 170 C and 180 C.) The determination of the time required to reach 90% of the maximum module level at a given temperature is done on a rheometer of the ARE type, the frequency of solicitation has been fixed. at 10 rad / s and the deformation at 5% The mechanical properties such as modulus, stress and elongation at break of the crosslinked compositions containing different concentrations of polymer (A) (Lotader) and polymer (B) ( Lotryl) are shown in Table 1 below: Composition 1 2 3 4 5 6 7 Lotader AX8900 (%) 99.5 89.5 79.5 69.5 59.5 49.5 39.5 Lotryl 28MA07 (%) BF3-monoethylamine (%) 0.5 0.5 0.5 0.5 0.5 0.5 0, 5 Young's modulus 7.4 7.7 8.4 9.4 10.8 11.6 13.1 Stress at break (MPa) 1.3 1.9 2.4 3.3 5.3 8, 3 8,7 Elongation at Break (%) 34.5 63.4 80.4 125.2 187.8 252 368 Figure 1 gives the graphical representation of the results in Table 1. As shown in Figure 1, the system reticulated based on 100% lotader AX8900 has a very low stress and elongation at break.

By comparison, if reference is made to a peroxide-cured ethylene-vinyl acetate system, the elongation at break is of the order of 650% and the tensile stress of 20 MPa for a Young's modulus equal to 15 MPa. To approach the results of a reference system, the Lotader i cationic initiator system was modified by adding Lotryl. Figure 1 clearly shows that from 30% Lotryl in the system, the module goes back above 1OMPa and 2908777 the elongation at break is doubled compared to the system without lotryl. From 50% of Lotryl, the elongation at break becomes greater than 250%, which is quite acceptable for flexible non foamed materials having a modulus around 10 MPa. Thus, the mechanical properties of non-foamed flexible materials can be transposed to soft foamed materials. The values of the time required to reach 90% of the maximum modulus level for Lotader -Lotryl-epoxidized soybean oil and initiator compositions at a given temperature are shown in Table 2 below: Composition 1 4 8 9 10 Lotader 8900 (%) 99.5 69.5 67.5 64.5 59.5 Lotryl 28MA07 (%) BF3-monoethylamine (%) 0.5 0.5 0.5 0.5 0.5 Ecepox PB3 (%) 0 0 2 5 10 t9o % to 150 C (s) 2001 2271 1521 2062 t90% to 160 C (s) 891 1143 1116 621 846 t90% to 170 C (s) 426 708 471 351 426 t90% to 180 C (s) 231 288 276 141 232 Figure 2 gives the graphical representation of the results of Table 2. As shown in Figure 2, the addition of 30% lotryl in a lotader and initiator system induces a decrease in the kinetics of crosslinking. For example, at 160 C, 14 without Lotryl, it takes 891 seconds to reach 90% of the maximum module level whereas with Lotryl it takes 1143 seconds. As shown in Figure 2, the addition of Ecepox up to 5% accelerates the kinetics of the system containing 70% lotader AX8900 and 30% Lotryl 28MA07, and whatever the test temperature.

We also note that there is an optimum of Ecepox content between 5% and 10% which accelerates the kinetics of crosslinking of the system. Table 3 indicates the mechanical properties such as modulus, stress, and elongation at break of the crosslinked compositions containing different concentrations of epoxidized soybean oil. (Ecepox PB3) 2908777 11 Composition 8 9 10 Lotader AX8900 (%) 67.5 64.5 5.5 Lotryl 28MA07 (%) 30 30 BF3-monoethyl amine (%) 0.5 0.5 0.5 Ecepox PB3 (%) 2 Young's modulus 7.6 7.8 7.5 Breaking stress (MPa) 2.6 2.8 2.5 Elongation at break (%) 119.5 127.6 125.1 25 35

Claims (13)

  1. Use of a composition for obtaining a crosslinked foam, said composition comprising: (A) a copolymer of ethylene and an unsaturated monomer bearing at least one epoxide group and optionally (meth) alkyl acrylate or vinyl carboxylate; (B) a copolymer of ethylene and alkyl (meth) acrylate or vinyl carboxylate; (C) a polymerization initiator and; (D) a pore-forming agent.   2. The use according to claim 1, wherein the unsaturated epoxide of the copolymer (A) is glycidyl (meth) acrylate and the alkyl (meth) acrylate of the copolymer (A) is chosen from (meth) acrylate. methyl, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate.   3. Use according to claim 1 or 2 wherein the (meth) acrylate of the copolymer (B) is selected from methyl (meth) acrylate, ethyl acrylate, n-butyl acrylate , isobutyl acrylate, 2-ethylhexyl acrylate.   4. Use according to one of claims 1 to 3 wherein the polymerization initiator (C) is an initiator of ionic type, preferably of cationic type.   5. Use according to one of claims 1 to 4 further comprising at least one compound (E) of plasticizer type El or E2 fluidifying.   6. Use according to claim 5 wherein the plasticizer El is chosen from 3o phthalates, adipates, alkyl benzoates, the alkyl chain having a carbon number greater than 6.   7. Use according to claim 5 wherein the fluidifier E2 is chosen from aliphatic or naphthenic oils.   8. Use according to one of claims 1 to 7 wherein the content by weight of the compound (B) relative to the total weight of the composition is at least 10%, preferably in the range of 25% at 75% by weight, or preferably in the range of 30 to 60%.   9. Use according to one of claims 1 to 8 wherein the content by weight of the polymerization catalyst (C) relative to the total weight of the composition is from 0.01% to 5%, preferably in the range from 0.1% to 2% by weight.   10. Use according to one of claims 1 to 9 wherein the content by weight of the compound (E) relative to the total weight of the composition is from 0.5% to 15% by weight, preferably in the range from 2% to 10% by weight, preferably in the range of 2 to 6%.   11. Use according to one of claims 1 to 10 further comprising other additives selected from mineral fillers, reinforcements, flame retardants and dyes.   12. Use of a flexible foam according to one of claims 1 to 11 in the field of automobiles, transport vehicles, building.   13. Use of a flexible foam according to claim 12 as a sound insulating element, seal, and / or automotive door seal.