JPS6114221A - Production of thermoplastic polyurethane of excellent mold resistance - Google Patents

Abstract

PURPOSE:To produce the titled polyurethane, by reacting a specified polyester- diol with an organic diisocyanate at a predetermined ratio and chain-extending the prepolymer. CONSTITUTION:A hydroxyl group-terminated polyesterdiol (of an MW of 800- 1,500) is obtained by reacting 3-methyl-1,5-pentanediol with a dicarboxylic acid (e.g., adipic, succinic or sebacic acid). Said polyesterdiol is reacted with an organic diisocyanate (e.g., 4,4'-diphenylmethane diisocyanate) in an amount satisfying the relationship (wherein M is the average MW of the polyester-diol and R is a molar ratio of the organic diisocyanate to the polyester-diol) at a temperature <=about 120 deg.C, and the obtained isocyanate-terminated prepolymer is reacted with a chain extender (e.g., 1,4-butanediol) at about 50-160 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing thermoplastic polyurethane having excellent mold resistance.

Conventionally, polyurethane has been produced by reacting polyols such as polyester polyols and polyether polyols with polyisocyanates and, if necessary, low-molecular compounds such as active hydrogen atoms. The materials used had poor hydrolysis and mold resistance, and as a result, the surface became sticky or cracked in a relatively short period of time under hot and humid conditions. However, there will be some restrictions on its use. Polyurethane containing polyether polyol (+1) instead of polyester polyol is fully satisfactory in terms of hydrolysis resistance and mold resistance, but on the other hand, it has very poor light resistance and also has poor mechanical properties and abrasion resistance. This also causes problems in terms of oil and solvent resistance.

On the other hand, conventional polyester polyurethanes with relatively good hydrolysis resistance include those using polycaprolactone polyol, and those obtained from 1,6-hexanediol, neopentyl glycol, and adipic acid. Products using polyester polyols are known, but these polyurethanes also have satisfactory hydrolysis resistance, and they cannot be said to have excellent mold resistance.

Conventional methods for preventing the deterioration of polyester polyurethane due to mold include adding fungicides such as pentachlorophenol and bis(tri-n-butyltin) oxide. It is possible to do so. However, in the polymerization method that does not use a hot medium, which is adopted as a method for producing thermoplastic polyurethane, if a fungicide is added at the beginning of the reaction, there is a possibility that a reaction between the fungicide and the organic diisocyanate will occur. Furthermore, the method of adding a fungicide to polymerized polyurethane has limited use because it is difficult to uniformly mix the fungicide with the polyurethane.

It is difficult to expect that fungicides will improve the mold resistance of thermoplastic polyurethane.

The inventors of the present invention have found that they have particularly excellent mold resistance, are inexpensive, have excellent hydrolysis resistance, have excellent transparency, have good moldability, and have excellent mechanical properties, oil resistance, abrasion resistance, As a result of research to obtain a thermoplastic polyurethane that has all the characteristics of cold resistance, we found that 3-methyl-
An average molecular weight of 800 to 1 having a hydroxyl group at the end obtained by reacting 1,5-pentanediol and dicarboxylic acid
It has been found that the furnace can be achieved by using a polyol of 500 and an organic diisocyanate in a molar ratio expressed by the following formula (1) with respect to the polyester diol.

0.0'024M 0.27≦R≦0.0024M+1
．． 90 ...... (1) (Here, M represents the average molecular weight of polyester diol, R represents the molar ratio of organic diisocyanate to polyester diol) 3-methyl-1,5-pentanediol and dicarboxylic acid It has been reported in Japanese Patent Application Laid-Open No. 47-34494 that polyurethane obtained from a polyester diol having a hydroxyl group at the end obtained by reaction has excellent hydrolysis resistance.
It is described in Japanese Patent Application Laid-open No. 48-101496 and the like.

In polyurethane elastomers, hydrolysis resistance and mold resistance do not necessarily correlate. That is, it cannot be said that polyurethane using a polymer polyol, which is advantageous in hydrolysis resistance, is necessarily directly advantageous in mold resistance. In addition, regarding the relationship between polyurethane composition and mold resistance when polyols with the same average molecular weight are used, and the relationship between polyurethane composition and mold resistance when the average molecular weight of the polyol is varied, please refer to this article. has not been revealed at all.

In the present invention, if the molar ratio of organic diisocyanate to polyester diol (hereinafter referred to as R) is smaller than the range shown by formula (1), both mold resistance and hydrolysis resistance will decrease. Also, if R is larger than the range shown by formula (1),
The produced polyurethane is too hard and has a high melt viscosity, making it unsuitable for melt polymerization and having poor moldability. General polyester polyols such as polybutylene adipate diol and polycaprolactone diol have significantly poor mold resistance9, even within the range of R in formula (1) defined in the present invention9.
In addition, the polyurethane becomes hard, resulting in poor molding. However, when using the polyol of the present invention,
It was found that even when R was relatively large compared to other polyester polyols, it maintained good moldability and also had excellent mold resistance. In addition, by using polyester diol with an average molecular weight of 800 to 1,500, it not only has superior mold resistance compared to using polyester diol with an average molecular weight higher than that, but also has improved hydrolysis resistance. but.

It was revealed. If the average molecular weight is less than 800, the mechanical properties will be poor, so it is preferably 800 or more.

In the present invention, aliphatic dicarboxylic acids such as adipic acid, succinic acid, azelaic acid, and sebacic acid are suitable as dicarboxylic acids to be reacted with 3-methyl-1,5-pentanediol.

In addition, as an organic diisocyanate, 1, for example, 4.4'
-diphenylmethane diisocyanate, 2.4-tolylene diisocyanate, phenylene diisocyanate, 1
．． Aromatic diisocyanates such as 5-naphthylene diisocyanate and 3,3'-cyclo4,4'-diphenylmethane diisocyanate are used. With other diisocyanates, even if formula (1) is satisfied, the effects of the present invention cannot be fully exhibited.

Furthermore, in the synthesis of polyurethane, a low molecular compound having two active hydrogen atoms is usually used as a chain extender, but in the method of the present invention, the following active hydrogen atom compound is used. Representative examples of these active hydrogen atom-containing compounds include 1.4-butanediol, propylene glycol, 1.6-hexanediol, 1.4-bis(β-hydroxyethoxy)benzene, 1.4-cyclohexanediol, Examples include diols such as bis(β-hydroxyethyl) terephthalate and xylene glycol.

A particularly preferred combination of an organic diisocyanate and a chain extender is 4,4'-diphenylmethane diisocyanate and 1,4-butanediol, at which time the most favorable effects can be obtained.

As for the operation method for obtaining the thermoplastic polyurethane of the present invention, a melt polymerization method is used, for example, an average molecular weight of 8
00-1500 polymer diol and excess organic diiso7anate in advance at 120°C or below, preferably at 10°C.
After the reaction is completed at a temperature below 0°C and the terminal isocyanate is synthesized, a chain extender is added thereto, vigorously stirred and mixed, and the molten mixture is poured onto a plate or vat. For example, 50℃~16
Either by reacting at a temperature of about 0°C and then pulverizing, or by melt polymerizing the above molten mixture in a mixer such as a kneader with a powerful stirrer, or by continuous melt polymerization using a multi-screw extruder. Alternatively, a polymeric diol, an organic diincyanate, and a chain extender are combined in 1
A method is employed in which the reaction product is mixed at a temperature of 20° C. or less to become a solid state, and then pulverized using a 7.K kneader or the like, and then polymerized in the solid state. The thermoplastic polyurethane disstomer of the present invention can be obtained by these methods.

The thermal 0T plastic polyurethane obtained by the present invention has excellent mold resistance, hydrolysis resistance, transparency, and molding processability, and can be processed by injection molding and extrusion molding at 150 to 230°C. This polyurethane can be used in sheets, films, hoses,
Tubes, belts, rolls, gears, anti-vibration agents, cushioning materials,
It is useful for backing materials, shoes, artificial leather, cushioning materials, mechanical parts, automobile parts, elastic fibers, and various other fields.

Next, the present invention will be explained in more detail with reference to Examples. In the examples, regarding the evaluation of mold resistance, a molded polyurethane film with a thickness of 200 μm was attached to a glucose peptone agar culture medium, and a mixed spore suspension of five types of molds was inoculated. The cells were cultured at 30° C. and humidity [90 to 95%], and the state of surface deterioration was observed. Please note that this test includes J.
IS Z ・2911-1960 Mold resistance test description Aspergillus niger ATCC9642, Penicillium luteum ATCC9644, Rhizogenes nigricans S, N, 32, Trichoderma T-I AT
CC9645, Ctomium bosum ATCC620
The resistance to hydrolysis using five types of molds in Section 5 was determined by performing a hydrolysis acceleration test on Boliurethane film in hot water at 100°C for one week, and then dissolving this sample in DMF to determine the retention of logarithmic viscosity. It was evaluated based on the percentage.

The raw materials used in the present invention are indicated by abbreviations, and the relationship between the abbreviations and the compounds is as follows.

Examples 1 to 7 Comparative Examples 1 to 6 Polyester diols of various molecular weights, MDI, and chain extenders were mixed in a kneader at 60° C. based on the compositions shown in Table 1, and polymerized.

At this time, as the polymerization progresses, the mixture becomes solid, but if it is further mixed in a kneader, the solid will be pulverized.

Thereafter, the reaction was allowed to proceed in powder form at a temperature of 100°C to obtain a high molecular weight polyurethane powder.

As is clear from the results in Table 2 and above, according to the present invention!
'7 Polyurethane is made by using polyvarnish 5-A/diol, which has a relatively low molecular weight! 0. Furthermore, it has excellent not only mold resistance but also hydrolysis resistance.

Claims (1)

[Claims] When producing thermoplastic polyurethane from a polymeric diol, an organic diisocyanate, and a chain extender, the polymeric diol is obtained by reacting 3-methyl-1,5-pentanediol with a dicarboxylic acid, and a hydroxyl group is added to the terminal. Using a polyester diol having an average molecular weight of 800 to 1,500, organic diisocyanate is added to the polyester diol in an amount of 0.0024M+0.27≦R≦0.
0024M+1.90 (where M is the average molecular weight of the polyester diol and R is the molar ratio of the organic diisocyanate to the polyester diol) A thermoplastic with excellent mold resistance characterized by being used at a molar ratio of Polyurethane manufacturing method.