JPS6352045B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polyurethane elastomer, and particularly to a method for producing a polyurethane elastomer using a specific high molecular weight diol. In a method for producing a polyurethane elastomer by using a high molecular weight diol, a chain extender, and a polyisocyanate compound as essential raw materials and reacting them in the presence of a catalyst, etc. by a prepolymer method, a semi-prepolymer method, a one shot method, etc., a high molecular weight polyol Polyoxytetramethylene glycol is often used as a solvent. Polyoxytetramethylene glycol provides a polyurethane elastomer with superior physical properties compared to alkylene oxide addition polymerized polyether polyols such as polyoxypropylene glycol, and is a polyurethane elastomer with particularly excellent tensile strength and abrasion resistance. It is characterized by the fact that it can be obtained. but,
Polyurethane elastomers obtained using polyoxytetramethylene glycol tend to become cloudy and are not suitable as polyurethane elastomers for applications requiring transparency.
For example, it is unsuitable for application to a polyurethane elastomer as an interlayer film in laminated glass or a bilayer layer in bilayer glass because of its transparency. In addition, polyoxytetramethylene glycol has a high freezing point, making it difficult to uniformly mix it with chain extenders and polyisocyanate compounds during the production of polyurethane elastomers. Of course, polyoxytetramethylene glycol is more expensive than polyether polyols made from alkylene oxides, such as polyoxypropylene glycol, and is not economically viable for widespread use. The present inventor investigated solutions to the above problems by modifying polyoxytetramethylene glycol with alkylene oxide. Polyether polyols obtained by randomly copolymerizing tetrahydrofuran, which is a raw material for polyoxytetramethylene glycol, and alkylene oxides such as ethylene oxide are known. However, in the case of a polyether diol made of a copolymer of tetrahydrofuran and ethylene oxide, for example, if the proportion of oxyethylene groups is high, the water absorption of the polyurethane elastomer becomes high, the water resistance becomes low, and the freezing point of the polyether diol almost decreases. First, if the proportion of oxyethylene groups is low, it will not be much different from polyoxypropylene glycol, and none of the above problems will be solved. Furthermore, in the case of a copolymer of tetrahydrofuran and propylene oxide, the mechanical strength or abrasion resistance of the polyurethane elastomer is significantly reduced. In addition, copolymerization of tetrahydrofuran and alkylene oxide involves problems such as catalysts that have not yet been fully resolved, and its production has not been easy. The present inventor has discovered that by adding alkylene oxide to polyoxytetramethylene glycol, it is possible to easily produce a block copolymer of both, and by using ethylene oxide and other alkylene oxides together in a specific ratio as the alkylene oxide, excellent properties can be obtained. It has been found that a polyurethane elastomer having the following properties can be obtained. The other alkylene oxides mentioned here are propylene oxide and butylene oxide, and both can be used in combination. The specific polyether diol in the present invention can be used alone as a high molecular weight polyol to produce an excellent polyurethane elastomer, but it can also be used in combination with other high molecular weight polyols. In particular, this particular polyether diol is suitable for applications such as laminated safety glass, which requires transparent polyurethane-based elastomers, which are not available using conventional polyoxytetramethylene glycols; It is suitable for use in place of polyoxytetramethylene glycol in applications where polyoxypropylene glycol has excellent physical properties, where tetramethylene glycol has been used. The gist of the present invention is a method for producing a polyurethane elastomer using this specific polyether diol, namely, producing a polyurethane elastomer using a high molecular weight polyol, a chain extender, and a polyisocyanate compound as essential raw materials. In the process, at least a portion of the high molecular weight polyol has a molecular weight of about 1200 obtained by mixing and/or sequentially adding ethylene oxide and propylene oxide and/or butylene oxide to a polyoxytetramethylene glycol having a molecular weight of at least about 300.
~6000 polyether diol, the oxytetramethylene group content in the polyether diol is approximately 20 to 70% by weight, and the oxyethylene group/
A method for producing a polyurethane elastomer, characterized in that the weight ratio of (oxypropylene groups and/or oxybutylene groups) is about 50/50 to 85/15. It is. The polyether diol in the present invention is produced by reacting a previously produced polyoxytetramethylene glycol with an alkylene oxide in the presence of a catalyst such as an alkali catalyst. Ethylene oxide and propylene oxide or butylene oxide are used as alkylene oxides,
Particularly preferred is the use of ethylene oxide and propylene oxide. As butylene oxide, 1,2-butylene oxide is particularly preferred, but 2,3-butylene oxide is particularly preferred.
-Butylene oxide may also be used. Moreover, propylene oxide and butylene oxide can be mixed and used together, or butylene oxide can be reacted sequentially with ethylene oxide and propylene oxide. Hereinafter, a combination of ethylene oxide and propylene oxide will be explained as a representative example of a combination of ethylene oxide and another alkylene oxide, but a part or all of propylene oxide can be replaced with butylene oxide. When polyoxytetramethylene glycol is reacted with ethylene oxide and propylene oxide, both alkylene oxides can be reacted in a mixed manner or sequentially. When reacting sequentially, any alkylene oxide may be reacted first. Further, ethylene oxide and propylene oxide can be reacted sequentially in multiple steps, or a mixture of ethylene oxide and propylene oxide and at least one of both polyols can be reacted sequentially.
The most preferred method is to react polyoxytetramethylene glycol with a mixture of ethylene oxide and propylene oxide. The molecular weight of polyoxytetramethylene glycol, which is the target of alkylene oxide addition reaction, is at least
300; if it is less than this, the resulting polyurethane elastomer will not have satisfactory tensile strength or abrasion resistance. For the same reason,
If the proportion of oxytetramethylene groups in the polyether diol obtained by adding alkylene oxide is less than 20% by weight, a good polyurethane elastomer cannot be obtained. The molecular weight of polyoxytetramethylene glycol is preferably 500 or more, particularly preferably 600 to 2,500. It is also preferred that the proportion of oxytetramethylene groups in the polyether diol is at least 30% by weight. On the other hand, the proportion of oxytetramethylene groups is 70
If it exceeds % by weight, it will be difficult to obtain a transparent polyurethane elastomer, and the solidification point of polyether diol will be high, close to that of polyoxytetramethylene glycol of the same molecular weight. A more preferable proportion of oxytetramethylene groups is 65% by weight or less. The ratio of oxyethylene groups and oxypropylene groups produced by the addition reaction of ethylene oxide and propylene oxide in polyether diol is 50/50 to 85/15, expressed as a weight ratio of both groups. It is necessary. When the proportion of oxyethylene groups is lower than this, the tensile strength and abrasion resistance of the resulting polyurethane elastomer tend to decrease significantly, and when the proportion of oxyethylene groups is higher than this, water absorption is high and water resistance is low. At the same time, the freezing point of the polyether diol also becomes high. The molecular weight of the polyether diol in the present invention is approximately 1,200 to 6,000, particularly preferably approximately 1,600 to 4,000, particularly preferably approximately 1,600 to 3,000. This polyether diol can be used alone or in combination with a high molecular weight polyol that is a raw material for polyurethane elastomers. It can also be used in combination with other high molecular weight polyols, in which case the proportion of this polyether diol in the total high molecular weight polyol is at least 30% by weight, preferably at least
Preferably it is 40% by weight. Other high molecular weight polyols include polyether polyols such as polyoxyalkylene polyols and polyoxytetramethylene glycol, polyester polyols, polycarbonate polyols, and hydrocarbon polyols such as polydienes having two or more hydroxyl groups. Particularly preferred high molecular weight polyols that can be used in combination are polyester diols and polycarbonate diols, whose molecular weights are at least
800, particularly preferably 1200 to 6000. As the chain extender, polyhydric alcohols, alkanolamines, polyamines, and other low molecular weight active hydrogen compounds having a valence of two or more are used. For example, ethylene glycol, propylene glycol, 1,4
-butanediol, glycerin, trimethylolpropane, N-alkyl dialkanolamine,
Examples include dialkanolamine, trialkanolamine, aromatic diamine, and halogen-containing aromatic diamine. Particularly suitable are dihydric alcohols and aromatic diamines. As the polyisocyanate compound, non-yellowing diisocyanates are particularly preferred from the viewpoint of producing transparent polyurethane elastomers. A non-yellowing diisocyanate is a diisocyanate compound that does not have an isocyanate group in its aromatic nucleus, and includes, for example, xylylene diisocyanate. Preferred non-yellowing diisocyanates are alicyclic or aliphatic diisocyanates, such as methylene bis(cyclohexyl isocyanate), isophorodiisocyanate, cyclohexylmethane diisocyanate, hexamethylene diisocyanate, and the like. In applications other than polyurethane elastomers for laminated safety glass, more common aromatic polyisocyanates can be used, such as diphenylmethane diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, and polymethylene polyphenyl isocyanate. These polyisocyanate compounds may be modified products, such as prepolymer-type modified products, carbodiimide-modified products, urea-modified products, Biuret-modified products, and the like. In the present invention, the polyurethane elastomer is obtained by reacting the above-mentioned three essential raw materials, and this reaction is usually carried out in the presence of a catalyst. As the catalyst, an organometallic compound such as an organotin compound or an amine catalyst such as a tertiary amine is used. Besides the catalyst, any additives can be used,
For example, ultraviolet absorbers, light stabilizers, antioxidants,
Colorants, etc. Furthermore, in applications where transparency is not required, fillers, reinforcing agents, etc. can also be used. The additives are not limited to these, and various additives may be added depending on the purpose. Synthesis Example 1 In a 5-volume stainless steel pressure-resistant autoclave, 2000 g of polyoxytetramethylene glycol (PTG-200, manufactured by Nippon Polyurethane) with a molecular weight of 1000,
25 g of a 48% caustic potassium aqueous solution was charged under a nitrogen atmosphere. This was heated to 120°C, and water was distilled off under reduced pressure. Next, 2250g of a mixture of propylene oxide and ethylene oxide in a weight ratio of 40/60 was heated at a temperature of 120%.
The cells were introduced for 2 hours while being maintained at ℃. Furthermore
The temperature was maintained at 120°C for 1 hour, and the unreacted oxide mixture was distilled off under reduced pressure. Magnesium silicate was added to adsorb the catalyst, filtered and dried to obtain a product.
The hydroxyl value of the obtained polyol was 57.1mgKOH/
It was a colorless liquid of 1.5 g. Synthesis Examples 2 to 7, Comparative Synthesis Examples 1 to 2 Table 1 shows the results of reactions performed in the same manner as in Synthesis Example 1 using various combinations of polyoxytetramethylene glycols and oxides. As can be seen from the results in Table 1, polyols synthesized from appropriate ranges of PO or BO/EO ratio and oxytetramethylene group content have a freezing point similar to that of polyoxytetramethylene glycol or polyoxytetramethylene glycol with the same molecular weight. It can be seen that this is reduced compared to the polyol in which only EO was subjected to an addition reaction. Examples 1 to 5, Comparative Synthesis Examples 1 to 3 To 100 parts of the polyol synthesized in Synthesis Examples 1 to 5 and Comparative Synthesis Examples 1 to 2 and commercially available polyoxytetramethylene glycol (PTG500), 4,4'-diphenyl was added. 77.8 parts of methane diisocyanate (MDI) was added, and the mixture was maintained at 80° C. for 3 hours with stirring under nitrogen to obtain a prepolymer. 22.2 parts of 1,4-butanediol was added to the prepolymer whose temperature was adjusted to 70°C, defoamed under reduced pressure while stirring, poured into a mold at 80°C, and cured at 120°C for 16 hours. The obtained polyurethane elastomer sheet was heated at 25℃ and humidity.
After aging for 7 days at 50% condition, various physical properties were measured. The results obtained are shown in Table-2. From the results in Table 2, it can be seen that the physical properties of the elastomers of Examples 1 to 5 are excellent in the balance of mechanical strength, abrasion resistance, and water absorption. That is, Comparative Example 1 has a low water absorption rate but poor mechanical strength, and Comparative Example 2 has a significantly high water absorption rate. Example 6, Comparative Example 4 Synthesis Example 2 and 100 parts of PTG500 (polyoxytetramethylene glycol manufactured by Nippon Polyurethane),
Methylenebis(cyclohexyl isocyanate)
79 parts were added thereto, and the mixture was maintained at 80° C. for 3 hours with stirring under nitrogen to synthesize a prepolymer. Add 1 to the above prepolymer heated to 70°C.
A urethane elastomer was produced in the same manner as in the previous example by adding 21 parts of 4-butanediol. The results obtained are shown in Table 3. From Table 3, it can be seen that the urethane elastomer using the synthetic polyol according to the present invention (Synthesis Example 2) is transparent, and furthermore, the mechanical strength is almost equivalent to that of commercially available polyoxytetramethylene glycol.

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Claims (1)

[Claims] 1. A method for producing a polyurethane elastomer using a high molecular weight polyol, a chain extender, and a polyisocyanate compound as essential raw materials, in which at least a portion of the high molecular weight polyol is a polyoxytetramethylene glycol having a molecular weight of at least about 300, mixed with ethylene oxide and propylene oxide. and/or butylene oxide and/or by sequential addition, the molecular weight of approximately
1200 to 6000 polyether diol, the oxytetramethylene group content in the polyether diol is 20 to 70% by weight, and the weight ratio of oxyethylene group/(oxypropylene group and/or oxybutylene group) is 50/50. A method for producing a polyurethane elastomer, characterized in that the polyurethane elastomer is 85/15.