SU931110A3 - Process for producing flexible foamed polyurethane - Google Patents

Abstract

1510383 Polyurethane foam BEROL KEMI AB 1 Oct 1975 [2 Oct 1974] 40155/75 Heading C3R A polyurethane foam having a low degree of hardness and high hydrophilicity is prepared by reacting a polyisocyanate in the presence of a catalyst, blowing agent at least partly consisting of water and foam stabilizer with a mixture of at least two mutually insoluble, at least tri-functional polyether polyols, the polyol mixture having a hydroxyl number of 35 to 45, the proportion of primary hydroxyl groups in the polyol mixture being more than 55% and not more than 80% of the total number of hydroxyl groups in the polyol mixture, the polyol mixture containing 50-70% wt. of CH2CH2O units, and the amount of polyisocyanate and polyol mixture being such that the NCO index is 0À85 : 1 to 1À05 : 1. Preferably one of the polyols is soluble in water and preferably has an HLB value of at least 15 and a turbidity point of at least 88‹ C. and an average molecular weight of 3000 to 5000. The other polyol should preferably have an HLB value not exceeding 5 and a turbidity point of below 70‹ C. and an average M.Wt. of 3000 to 7000. The polyether polyols can be obtained by adding at least 2 different alkylene oxides, one of which is ethylene oxide and the remainder being preferably propylene oxide and/or butylene oxide; to a nucleus having at least 3 reactive hydrogens, e.g. glycerol, trimethylolpropane or triethanolamine, either as mixtures of alkylene oxides or separately in one or more batches. Suitable polyisocyanates are toluene diisocyanate, hexamethylenediisocyanate, diphenylmethanediisocyanate and polyphenylpolymethylenepolyisocyanate. The catalyst may be a tertiary amine and/or an organo-metal compound. In the examples foams are prepared from formulations comprising an 80/20 mixture of 2,4- and 2,6- toluene diisocyanate, water and optionally trichlorofluoromethane, a silicone oil foam stabilizer, triethylenediamine and dimethylaminoethanol as catalysts, and a polyether polyol mixture which is a mixture of two different reaction products of glycerol with ethylene oxide and propylene oxide.

Description

3 taking into account that the remaining alcohol oxides are propylene oxide, butylene oxide or a mixture of these oxides. Alcohol oxides are made by conventional methods. Ethylene oxide and alcohol oxide with a higher molecular weight can be added either in a mixture or individually in one or several steps. To obtain a high degree of softness, it is necessary that the two polyether alcohols be mutually insoluble, i.e. so that they have a different degree of hydrophilicity. Thus, one of the polyhydric alcohols should be soluble in water and preferably should have a liLB of at least 15 and a cloud point of at least 88 C. Its average molecular weight is 3000-5000. Another polyether polyhydric alcohol must be significantly more hydrophobic and have a HLB index not exceeding 5 and the cloud point lower. The average molecular weight may be slightly higher and range from 3000 to 7000. Polyhydric alcohols are prepared as follows. a) K 92 weight.h. glycerol is first added 000 weight.h. propylene oxide and then 1300 weight.h. ethylene oxide. The resulting polyether polyhydric alcohol has a hydroxyl number of 36 and 75% of the primary hydroxyl groups. . . b) To 92 weight.h. glycerol is first added 470 parts by weight. propylene oxide and then weight.h. mixtures containing 18 propylene oxide and 82% ethylene oxide. The resulting polyether polyhydric alcohol has a hydroxyl number of 42 and 58% of the primary hydroxyl groups. c) To 134 weight.h. trimethylpropane was first added 3000 parts by weight. mixtures containing 18% propylene oxide and 82% ethylene oxide, then 300 parts by weight propylene oxide and finally, 350 weight.h. ethylene oxide. The polyhydric alcohol obtained has a hydroxyl number equal to 42 and the percentage of hydroxyl groups equal to 73 d) K 99 parts by weight glycerol is first added 5000 parts by weight. oxide propyl on and then 700 weight.h. ethylene oxide. The resulting polyhydric alcohol has a 04 hydroxyl number of about 34 and a percentage of primary hydroxyl groups of 75%. Used in accordance with the proposed method, the polyisocyanate must have at least two functional groups, for example, it may be toluene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, polyphenylpolymethylene polyisocyanate, and a mixture of these compounds. The preferred isocyanate is toluene diisocyanate, which may be isomers: the 2,4-form or the 2,6-form, or a mixture of the mentioned isomeric forms. A suitable mixture of isomers contains about 80% of the 2,4-isomer and 20% of the 2,6-isomer, but other proportions of the isomers can be successfully used. The amount of isocyanate added must be selected in accordance with the remaining components contained in the reaction mixture so that the isocyanate index, i.e. the ratio between isocyanates and hydroxyl groups in the reaction mixture was 0.85-1.05, preferably 0.90-0.98. The reaction between the isocyanate and the polyether polyhydric alcohol is carried out in the presence of an amine as a catalyst, which is usually a tertiary amine, such as, for example, triethylenediamine, dimethylaminoethanol and etramethylethylenediamine. Organometallic compounds, for example, tin 2-ethylhexanate, tin dibutyldilaurate, lead naphthenate or cobalt can also be used as catalysts. The latter are preferred in small amounts and in combination with amines-catalysts. The formation of the cells and, therefore, the density of the polyurethane foam is controlled by controlling (by conventional means) the amount of added water and any other blowing agent, for example, trichlorofluoromethane or methylene chloride. Adding foam stabilizers, such as silicone oil, provides good foam stability and good physical performance. In addition to the additions (additives), other additives can be added, if necessary, using any known method. Examples 1-3. Using a five-component laboratory injection machine, polyether polyhydric alcohol of type a) is mixed with polyester polyhydric alcohol of type b), water, silicone oil, triethylenediamine, dimethylaminoethane and trichlorfluoromethane in the weight ratio indicated in Table. In addition, tolu old diisocyanate (80% 2, -isomer and 20, 2,6-isomer) is added to the mixture in such a quantity, where the isocyanate index is 0.95. The mixture is poured into a mold having dimensions 50x50x30 cm, in which at room temperature, the final foamed plastic is obtained every other day. After 2 hours at room temperature, the resulting product had the following physical characteristics. Table 1 Polyether type polyhydric alcohol, a) 25 25 25

Physical characteristics CASIT.ffi)

Density, kg / m 19.7 Strength

at break, 1.2 The coefficient of elongation at break, weight. 430 Tear resistance, kg / cm 0,5

Components, parts by weight

Examples

I 4 I 5

Polyether polyhydric alcohol d)

Polyether polyhydric alcohol b)

Water

Silicone oil Triethylenediamine (33) Dimetyamo noetha nol 0 Residual deformation at 90% compression, 10 10 10 Resilience at impact,% 50 50 50 Hardness at 25% compression, Kp / dm 0,6 0,9 1, 1 Hardness at 65% compression, Kp / dm 1.2 1.7 2.1. From the results it can be seen that the resulting foams have very low hardness. Their hardness refers to the hardness of the foam obtained according to a known method, with the same density and approximate physical characteristics as 1/2. Examples i and S Using a five-component laboratory foaming machine, polyester polyatomic alcohol type d) was mixed with polyester polyhydric alcohol type b), (these alcohols are mutually insoluble) with water, silicone oil, triethylenediamine and dimethylamine ethanol in a weight ratio indicated in Table 2 In addition, toluene diisocyanate (80% of the 2,4-isomer and 20% of the 2,6-isomer) is added in an amount where the isocyanate index is 0.95. The mixture is poured into a mold having a size of 50x50x30 cm, in which it remains for one day to obtain a foam. A study after 2 hours at room conditions of the physical properties of the foamed foam produced the following results. table 2

Physical Specifications (ASTWD156 -629)

Density, kg / m 29 29

Hardness at

 compression,

"P / dm 1,3 1,0

Hardness at

65% compression

Kp / dm 2.5 2.0

The obtained polyurethane foams, in addition to low hardness, have a uniform cellular structure | | oh,. high elongation at break and high tensile strength.

During the formation of the foamy structure, no volume change was observed.

Claims (1)

1. The patent of France, No. 2172860, cl. from 08 g 22/00, published 1971 (prototype).