FR2858622A1 - New flexible polyurethane foams based on polyester polyols containing particulate inorganic filler, having low density and shrinkage and useful for producing moldings, especially shoe mid soles - Google Patents

Abstract

New flexible polyurethane foams (A), based on polyester polyols (I), have density less than 0.3 g/cm 3>, dimensional shrinkage less than 5% and thickness reduction less than 5% and contain more than 1 wt. % of a particulate inorganic filler (II). An independent claim is included for the preparation of (A). a polyurethane foam (A), obtained from (I) and (II) and containing a particulate inorganic filler (III), including a stage of forming a dispersion of (III) in (I), (A') being formed by reacting the dispersion with (II) in presence of a catalyst and a foaming agent.

Description

Polyurethane foam, polyester-polyols for obtaining foams and

use of these foams

  The present invention relates to polyurethane foams especially used for the manufacture of molded articles such as soles for different types of shoes.

  It relates more particularly to a low density polyurethane foam having mechanical properties suitable for the application of soles of shoes and more particularly for the soles of sports shoes.

  Polyurethane foams are used in many applications and can be classified into two types, rigid foams and flexible foams. The field of the present invention relates to flexible polyurethane foams.

  One of the important applications of these flexible foams is the manufacture of soles for shoes, especially for sports shoes, and women's shoes of the platform type. More particularly, polyurethane foams are used for the manufacture of a part of a shoe sole called midsole or insole (more generally distinguished by the term "mid sole") In these applications, the sole must have a good compressive strength, high hardness and tear resistance, but also high rebound or resilience properties to provide elasticity, and to provide user comfort.

  Suitable polyurethanes have already been proposed for these applications.

  However, to obtain a level of suitable properties, it was necessary to produce the articles with a polyurethane foam of a certain density level leading to soles of higher weight than those obtained with a vinyl acetate copolymer (EVA) .

  There is a problem of being able to produce articles of polyurethane foam of very low weight, at least of the same order as those obtained with EVA while maintaining the level of properties of polyurethane foams; properties that are not obtained with EVA soles.

  It is also desired to improve the properties of polyurethane foams irrespective of the level of their density.

  One of the aims of the present invention is to propose a novel polyurethane-based foam having high properties at equivalent or lower density compared to polyurethane foams of the prior art, and a level and a compromise of properties suitable for applications in the manufacture of insoles of very low weight.

  Polyurethanes are obtained by reaction between a diisocyanate monomer and a diol monomer. In the case of polyurethane foams, the diisocyanate monomer is generally a prepolymer comprising terminal isocyanate functional groups while the diol monomer is a hydroxyl terminated polyesterdiol prepolymer.

  By way of illustration, the isocyanate monomers that are suitable for the invention are aromatic, cyclic, saturated and aliphatic polyisocyanates. The isocyanate monomers may also comprise a polyester polyol or polyether polyol chain with which two polyisocyanate molecules have reacted. In this case, it is usual to call these isocyanate monomers isocyanate prepolymers.

  Examples of isocyanate monomers include aromatic isocyanates, toluene diisocyanates, xylylene diisocyanate, polymethylene polyphenylene diisocyanate, saturated cyclic isocyanates such as hydrogenated methylene diphenyl diisocyanate, hydrogenated toluene diisocyanate, isophorone diisocyanate, aliphatic diisocyanates, and the like. such as hexamethylene diisocyanate and lysine diisocyanate.

  Modified isocyanate prepolymers include prepolymers obtained by reaction of a polyetherdiol or polyesterdiol with a diisocyanate, and more particularly the isocyanate prepolymers comprising a flexible segment formed by a polyoxyalkylene glycol which has reacted with methylenediphenyl diisocyanate. Such a compound is particularly advantageous for the manufacture of a low density foam.

  The polyester polyols may be produced by reaction between dicarboxylic acids comprising from 2 to 12 carbon atoms, preferably from 4 to 6 carbon atoms, and a polyol, preferably a diol.

  Examples of dicarboxylic acids include aliphatic diacids such as adipic acid, succinic acid, glutaric acid, suberic acid, azelaic acid, sebacic acid, aromatic acids such as as phthalic acids, isophthalic, terephthalic, naphthenic. These diacids can be used individually or as a mixture, especially the mixture of adipic acid, succinic acid, glutaric acid obtained as a by-product in the process for the manufacture of adipic acid by oxidation of cyclohexanol and / or cyclohexanone.

  It is also possible to use derivatives of these diacids such as diesters comprising from 1 to 4 carbon atoms for the alcohol radical, acid anhydrides and acid chlorides.

  Suitable polyols for the invention include glycols comprising from 2 to 10 carbon atoms, preferably from 2 to 6 carbon atoms such as ethylene glycol, diethylene glycol, 1,4 butanediol, and 1 to 6 carbon atoms. , Pentanediol, 1,6 hexanediol, 1,10-decanediol, 2,2-dimethyl-1,3-propanediol, 1,3-propanediol, dipropylene glycol. It is also possible to use esters of these diols with the diacids described above, especially those containing from 4 to 6 carbon atoms, the condensation products of hydroxycarboxylic acids such as hydroxycaproic acid, the products of polymerization of lactones. such as caprolactone, the most preferred polyesterdiols for the invention are ethanediol polyadipates, 1,4 butanediol polyadipates, 1,6 hexanediol-neopentyl glycol polyadipates, 1,6 hexanediol-1 polyadipates, 4 butanediol, and polycaprolactones. Polyesterdiols having a molecular weight of from 600 to 10,000 are preferred.

  According to a preferred feature of the invention, the inorganic filler particles may be incorporated into the polyester polyol by adding said particles to the reaction medium either by mixing with the polyol or directly in the mixture of polyol and diacids. The inorganic filler suspension in a polyester polyol is also an object of the present invention.

  According to a preferred embodiment of the invention and to obtain a stable suspension of the inorganic filler in the polyester polyol as well as an improved increase of the properties of the polyurethane foam, it is advantageous to add the inorganic filler in the medium. esterification reaction in mixture with the diacids or a portion of the diacids.

  This mixture can be obtained by mixing the granules or chips of diacids with the inorganic filler powder at room temperature, for example.

  It is also possible to coat the particles constituting the inorganic filler with part of the diacids. This coating is obtained by heating the mixture to a temperature above the melting or softening temperature of the diacids.

  It is also possible to add to this mixture other additives usually used in the formulation of polyurethane foams.

  Suitable inorganic particulate fillers for the invention include, for example, fillers having particles of size less than 60 μm, preferably less than 20 μm when dispersed in the polyurethane foam or polyester polyol.

  Thus, suitable fillers for the invention are aluminosilicate, silica, and titanium oxide powders, for example.

  According to a preferred embodiment of the invention, silicas are the preferred fillers and more particularly amorphous silicas, especially those obtained by precipitation. They are in the form of aggregated particles of size or diameter advantageously less than 50 .mu.m.

  Precipitated silicas are preferred since they may be in the form of agglomerated particles forming granules of size at least 50 μm or greater than 150 μm. These agglomerates disintegrate easily under the action of stirring force or shear to give particles smaller than a few microns, for example less than 5 microns, especially when mixing with diacids, or polyols.

  These agglomerates may be in the form of substantially spherical beads or granules, obtained for example by atomization, as described in European Patent No. 0018866. This silica is marketed under a generic name MICROPERLE. Such silicas which have remarkable properties of flowability, dispersibility and high impregnation capacity are especially described in European Patents 966207, 984773, 520862 and international applications WO95 / 09187 and WO95 / 09128.

  Other types of silicas may be suitable for the invention, such as those described in French Patent Application No. 01 16881 which are pyrogenic silicas or partially dehydroxylated silicas by calcination or surface treatment. These examples of silicas used as a solid mineral substrate are only described for guidance and as preferred embodiments. It is also possible to use other silicas obtained by other processes having properties of porosity and dispersibility suitable for carrying out the invention.

  The amount of inorganic filler present in the composition of the diacids can be very variable. Thus, the composition may comprise predominantly silica in which or on which is impregnated or deposited a diacid such as adipic acid, or a mixture of diacids (adipic, glutaric, succinic), hereinafter referred to as DBA. This impregnation can be obtained by melting the diacids and adding the silica or by any other means. The composition may also comprise silica impregnated with a diacid mixed with diacids in powders, chips, or granules.

  As indicated above, the mixture may be only a mixture of the inorganic filler powder, for example silica, with granules, powder or chips of diacids. This mixture is carried out at room temperature.

  The amount of inorganic filler in the suspension in the polyol or mixture with the diacids is selected according to the desired inorganic filler concentration in the polyurethane foam.

  Thus, concentrations of between 1 and 80% filler in the mixture with the diacids can be used.

  According to another subject of the invention, the polyesters polyols containing an inorganic filler are obtained according to a manufacturing process comprising two steps, a first esterification step and a second polycondensation step. The esterification step is carried out by mixing the diacids with polyols, for example a mixture of ethylene glycol and diethylene glycol with a diol / diacid molar ratio of between 1.2 and 1.5.

  The reaction temperature in this first stage is progressively increased during the progress of the reaction. By way of example, the beginning of the reaction is started at a temperature of 160 ° C. to reach a temperature of 220 ° C. at the end of the reaction.

  According to the invention, the diacids are added in admixture with the inorganic filler. The second polycondensation step is carried out with the addition of a catalyst such as tetrabutyl titanate (TBT) with a weight concentration of 0.003% relative to the weight of diacids employed. The polymerization temperature is 200 ° C. under a pressure of between 10 and 20 mbar.

  The polyester polyol obtained is characterized by the hydroxyl number (loH) corresponding to the number of mg of potassium hydroxide per gram of polyol to convert the hydroxyl functions to alkoxide and the acid number (IA) which represents the number of mg of KOH necessary to neutralize 1 g of polyol.

  Polyester polyol is also characterized by viscosity as well as its molecular weight.

  Advantageously, an additive limiting or preventing the hydrolysis of the ester functions is added in the polyol polyesters, such as carboimides such as cyanamides; cyanamide hydrogen; carbimides; cyanogenamides; amidocyanogenes.

  It may also be advantageous to add in the polyester polyols UV stabilizing additives such as hindered amines, antioxidants, flame retardants or the like.

  The polyurethanes of the invention are obtained according to the conventional and conventional methods.

  Thus, the polyester polyols of the invention are mixed with optionally a chain extender and the polyisocyanate in the presence of a foaming or pore forming agent and a catalyst.

  As a foam-forming agent, water, hydrocarbons, chlorofluorocarbons, hydrogenated fluorocarbons may be used alone or in admixture. Water is the preferred foam-forming or porogen-forming agent.

  Suitable catalysts for the invention include tertiary amines such as 1,4 diazabicyclo- (2,2,2) -octane N, N, N ', N' tetramethylhexamethylinediamine; N, N, N ', N' - tetramethylpropylene diamine; N, N, N ', N', N "pentamethyldiethylenetriamine, trimethylaminoethylpiperazine, N, N dimethylcyclohexylamine, N, N dimethylbenzylamine, N-methylmorpholine, N ethylmorpholine, triethylamine, tributylamine, bis (dimethylaminoalkyl) piperazine, N, N, N '; N, N, N'-tetramethylethylenediamine, N, N, ethylbenzylamine, bis (N, N, diethylaminoalkyl) adipate, N, N, N ', N' 1,3-tetramethylbutanediamine, N, N, dimethyl-phenylethyldiamine, 1, 2 dimethyl imidazole, 2-methylimidazole and the like Other catalysts can be used such as organometallic compounds such as dibutyl tin dilaurate, tin oleate, cobalt naphthenate, lead naphthenate.

  Other additives such as cell size and shape regulators, pigments, coloring agents, antioxidants can be added.

  The mixture is injected into a mold to form the polyurethane foam and obtain an article of the desired shape such as soles, for example.

  By adjusting the amount of foam-forming agent, for example the amount of water, it is possible to obtain foams of different densities, for example between 0.1 and 0.5 g / cm 3, advantageously between 0, 15 and 0.25 g / cm3.

  The compositions of the invention make it possible to obtain, in particular, low density polyurethane foams, for example of the order of 0.2 g / cm 3, leading to articles having properties that are suitable for applications such as shoe soles. These properties are particularly suitable for the manufacture of intermediate or inner soles (midsoles) for sports shoes, or other types of shoes.

  Indeed, for this type of application, the polyurethane sole must have a good level of hardness measured by standard methods ISO2439 or ASTM D2240. It is also important to determine the tensile strength determined according to ISO 1798/76. , elongation at break measured according to ISO1798 / 76 or ASTM D412.

  Other properties are also important for certain applications such as those for the production of intermediate midsole for shoes.

  The bulk density is determined according to ISO 845/77 OR ASTM D3574. The shrinkage during molding is measured according to ASTMD 3851.

  The tear resistance is accessible by the implementation of ASTM D3574 or ISO 8067 standards. The collapse of the foam or contraction of the cells is determined by measuring the decrease in the thickness of a sample.

  Finally, for sole application, it is important to determine the rebound ability of the sole representing the ability of the foam to resist compression. This property is determined according to ISO 1856/72 or ASTM D395.

  The properties of shrinkage, tensile strength, elongation at break, tear resistance are also important. The compositions of the invention make it possible to obtain articles having, in particular, high rebound and tear resistance properties enabling the production to be performed. intermediate soles for shoes, especially sports shoes. These insoles for improving the comfort of the shoes, with a sole weight equivalent to that of the EVA soles.

  In addition, the soles obtained with the compositions of the invention have improved lifetimes because the aging and fatigue resistance properties of the polyurethane foam limit the deterioration of the sole.

  These advantages and properties will appear more clearly in view of the examples given below for information only Comparative Examples 1: A test for producing a polyurethane foam from the formulations marketed by the company Dow Chemical under the name VORALAST GF422 for the polyol and VORALAST GS 749 for the isocyanate prepolymer.

  The polyurethane foam is obtained by mixing the products listed in Table I in the proportions by weight indicated.

O

Table I

  Product Density foam Normal low density foam (g) (g) Polyol 100 100 Chain extender (MEG) 14 8,17 Foaming agent (water) 0,1 0,64 Catalyst 1,2 1,57 Active surfactant 0, 2 0.47 Isocyanate prepolymer 129, 3 129.3 NCO / OH ratio 1.12 1.12 The properties of the foams obtained determined according to the standard methods described previously are indicated in the following Table II:

Table II

  Test Density Hardness Resistance Elongation Resistance to apparent (AsherC) tensile fracture% tear (g / cm3) kg / cm2 kg / cm 1 0.35 64 24.6 284 6.4 0.20 31 13 289 5.1 These tests clearly show the effect on the mechanical properties of a density drop of a polyurethane foam when the compounds used to form this foam are identical. I!

Example 2

  A polyurethane foam was obtained using as polyol, a polyester polyol prepared according to the following procedure and as isocyanate prepolymer the prepolymer of Example 1: In a first step of the adipic acid is added to a mixture of ethylene glycol (MEG) and diethylene glycol (DEG) containing 70% by weight of MEG.

  The molar ratio between the alcohols and the diacid is between 1.2 and 1.5.

  The reaction is carried out by heating the mixture at 160 ° C. for 1 hour and then raising the temperature in steps from 15 ° C. to 220 ° C. This reaction is carried out in an inert atmosphere, for example nitrogen.

  The esterifiat obtained is polycondensed in a second step after addition of tetrabutyl titanate (TBT) at a concentration by weight of 0.003% relative to the amount of diacid added.

  Polymerization is carried out at 200 ° C. under reduced pressure of 15 mbar. The polyester polyol obtained is characterized by the OH (loH) number and the acid number (IA) and the viscosity.

  In Example 2, the obtained polyester polyol has: A loH of 58 mg KOH / g polyol,> IA 4.2 mg KOH / g polyol> A viscosity of 5250 mPa.s at 35 ° C. .

  The polyurethane foam is obtained by mixing the following compounds and in the proportions indicated in Table III

TABLE III

  Products Proportion (g) Polyol 100 Chain extender (Ethylene glycol) 8.84 Water 1.00 catalysts 2.6 Active surfactant 1.0 Isocyanate prepolymer 145 NCO / OH 1.25 The properties of the resulting foam are:> Density: 0.21 / cm3> Hardness (AsherC): 52> Tensile strength: 15.4 kg / cm2> Elongation at break: 254%> Tear resistance: 5.09 kg / cm 10 Polyurethane foam has a high collapse of its thickness which represents 25% of the initial thickness.

  This percentage is evaluated by determining the initial thickness and the final thickness and calculating the percent decrease in thickness.

Example 3

  Example 2 is repeated but using an adipic acid / silica mixture in place of the adipic acid in the esterification step.

  The adipic acid / silica mixture is obtained by mixing granules of adipic acid with a silica powder marketed by Rhodia under the trade name TIXOSIL 365.

  Two tests are carried out with a silica concentration in the different adipic acid: Example 3A: 6% by weight of silica in the adipic acid / silica mixture Example 3B: 12% by weight of silica in the adipic acid / silica mixture.

  The characteristics of the polyester polyols obtained are:

Example 3A

  > IOH: 62 mg KOH / g polyol> IA: 3.07 mg KOL / g polyol> Viscosity: 5700 mPa.s at 35 ° C.

Example 3B

  IOH: 55.8 mg KOH / g polyol IA: 5.50 mg KOH / g polyol Viscosity: 13950 mPas at 35 ° C. Polyurethane foams were obtained using the compounds and proportions indicated in Table III above.

  The properties of the foams obtained are: Example 3A: Density: 0.23> Hardness (AsherC): 61> Tensile strength: 16.3 kg / cm 2> Elongation at break: 243%> Tear resistance: 4 , 24 kg / cm

Example 3B

  > Density: 0.22> Hardness (AsherC): 61> Tensile strength: 17.7 kg / cm2> Elongation at break: 344%> Tear resistance: 4.27 Kg / cm.

  The two polyurethane foams exhibiting remarkable dimensional stability.

  Indeed, the decrease in thickness is of the order of 2% of the initial thickness.

  Furthermore, the foam of Example 3A has a good compression or rebound resistance property equal to 5.5% and a shrinkage in width equal to 1.5% and in length equal to 0.57%.

Example 4

  Test 3A was repeated but using a mixture containing 75% by weight of adipic acid and 25% of a mixture of diacids obtained as a by-product in the process for the manufacture of adipic acid by oxidation of cyclohexane. To this mixture of diacids 6% by weight of silica TIXOSIL 365 was added as in Example 3A.

  The polyester polyol obtained has the following characteristics:> IOH: 62 mg of KOH / g polyol> IA: 3 mg of KOH / g polyol> Viscosity: 5 700 mPa · s at 35 ° C. The polyurethane foam obtained according to the indications given in Table III It has the following properties: Density: 0.21 g / cm3 Hardness (AsherC): 57 kg / cm2 Elongation at break: 312% Tear resistance: 3.9 Kg / cm 25 Compressive strength: 6% Removal : width: 0.62% length: 0.43%

Claims (15)

claims   A flexible polyurethane foam based on a polyester polyol characterized in that it has a density of less than 0.3 g / cm 3, a dimensional shrinkage of less than 5% and a sag of the thickness of less than 5% and that it comprises an inorganic particulate filler at a weight concentration greater than 1% by weight relative to the weight of foam.   2. Foam according to claim 1, characterized in that the density is less than 0.25 g / cm3, advantageously between 0.1 g / cm3 and 0.25 g / cm3.   3. Foam according to one of the preceding claims, characterized in that the inorganic particulate filler is selected from the group consisting of alumino-silicates, silicas, titanium oxides.   4. Foam according to claim 3, characterized in that the inorganic particulate filler is a precipitation silica.   Foam according to Claim 4, characterized in that the precipitated silica is in the form of a powder comprising particles of size less than 60 μm. Foam according to one of the preceding claims, characterized in that it comprises additives selected from the group consisting of pigments, colorants, thermal stabilizing additives and / or light 7. A method of manufacturing polyurethane foam according to one of claims 1 to 6 characterized in that it comprises: reacting a polyester polyol comprising an inorganic particulate filler dispersed and suspended in said polyester polyol with an isocyanate monomer; in the presence of a catalyst and a foam-forming agent 8. Process according to claim 7, characterized in that the polyester polyol is obtained by a process consisting of: In a first step, mixing the particulate inorganic filler with diacids.   > Carrying out the esterification or reaction between diols and the diacid / inorganic filler mixture,> And in a second step, polymerizing the products obtained in the esterification step 9. Process according to claim 8, characterized in that the concentration of inorganic filler in the diacid / filler mixture is between 1% and 80% by weight relative to the weight of the mixture.   10. A process according to claim 8 or 9, characterized in that the diacids are selected from the group consisting of adipic acid, glutaric acid, succinic acid, phthalic acids, and adipic acid mixtures. succinic / glutaric 11. The method of claim 10, characterized in that the concentration of adipic acid in the diacid mixture is greater than 40% by weight.   12. Use of polyurethane foam according to one of claims 1 to 6 for the manufacture of molded articles.   13. Use of polyurethane foam according to one of claims 1 to 6 for the manufacture of insole and / or intermediate shoe.   14. Foot midsole obtained by molding a polyurethane foam according to one of claims 1 to 6.   15. shoe comprising at least a portion of the polyurethane foam sole   according to one of claims 1 to 6.