JPH0693070A - Method for modifying and molding thermoplastic polyurethane resin - Google Patents

Abstract

PURPOSE:To obtain the polyurethane molded product stable in modification moldability and excellent in heat resistance by modifying and molding a polyurethane resin with a polyisocyanate compound preliminarily mixed with a specific oxidation stabilizer. CONSTITUTION:100 pts.wt. of a polyisocyanate compound is preliminarily mixed with 0.05-2 pts.wt. of a hindered phenol compound of the formula (R is t-butyl), mixed with a thermoplastic polyurethane resin, and subsequently thermally molded. The polyisocyanate compound is preferably a preliminary polymer produced by reacting diphenylmethane diisocyanate with a polyether polyol having a mol.wt. of 60-5000 and an NCO group content of 2-29wt.%. The polyether polyol is preferably poly(oxotetramethylene) glycol produced by the ring-opening polymerization of THF.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying and molding a thermoplastic polyurethane resin with a polyisocyanate compound. More specifically, the present invention relates to a method for stabilizing a modified formation by an additive and obtaining a polyurethane molded product having excellent heat resistance when a polyisocyanate compound is added to a thermoplastic polyurethane resin and mixed and molded.

[0002]

BACKGROUND OF THE INVENTION Thermoplastic polyurethane resins have excellent physical properties such as high tensile strength, fatigue resistance and good low temperature flexibility and abrasion resistance. Due to these characteristics, packings, various machine parts, automobile parts, electronic device parts, etc. are produced by injection molding, and also belt hoses, tubes, sheets, etc. are formed by extrusion molding. Furthermore, polyurethane elastic yarn is also produced by the melt spinning method. However, since the thermoplastic polyurethane resin basically has a linear structure,
Its heat resistance is inferior to that of thermosetting polyurethane resin, and its use in applications requiring heat resistance is limited. Therefore, in order to compensate for the above-mentioned drawbacks, a crosslinked structure is provided in the molecule of the thermoplastic polyurethane resin during or after molding,
For example, the following method is known as a method for converting the resin into a thermosetting resin or a polyurethane resin having a thermosetting property.

1) A method in which an isocyanate group-containing compound is mixed with a thermoplastic resin that does not react with the compound, the resulting mixture is blended with a thermoplastic polyurethane resin, and the blend is then subjected to a molding machine for molding ( Japanese Patent Publication 58-20
63). 2) When melt-spinning a thermoplastic polyurethane elastic material, a method in which a polyisocyanate compound having a molecular weight of 400 or more is added to the melted polyurethane resin and mixed, followed by spinning (JP-B-58-46573). 3) When thermoforming a thermoplastic polyurethane resin, a method of adding and mixing a polyisocyanate compound having a molecular weight of 300 or more to the polyurethane resin and molding the mixture (Japanese Patent Publication No. 1-2.
5328). 4) There is a method in which a thermoplastic diene resin is added with and mixed with a tolylene diisocyanate dimer and then thermoformed.

According to these methods, the urethane bond in the thermoplastic polyurethane resin and the isocyanate group of the polyisocyanate compound react to form an allophanate bond, and when a urea bond is present in the resin, a biuret bond is formed while crosslinking. It is a method of converting into a polyurethane resin having a structure, and is effectively used for modifying a thermoplastic polyurethane resin.

[0005]

However, in these reforming methods, various molding problems occur as the continuous operating time of the molding machine elapses. For example, in extrusion molding, fluctuations in tube diameter due to fluctuations in resin pressure,
Adhesion of infusible material to the tube surface, increase in filtration pressure in melt spinning, fluctuation in thread diameter and thread breakage, short shot in injection molding and generation of defective molding due to mixing of unmelted material, and the like. Further, in any of the moldings, it is also pointed out that, together with the above phenomenon, improvement of heat resistance is insufficient and a target product cannot be obtained.

Most of the reason for this is thought to be that the thermoplastic polyurethane resin and the polyisocyanate compound added as a modifier react intricately at high temperature, resulting in the formation of an insoluble material in the molding machine. However, it is often a problem especially in the case of polyether polyurethane resin. That is, the object of the present invention is to improve the continuous molding time by stabilizing the crosslinking reaction in the modified molding by adding and mixing the polyisocyanate compound of the thermoplastic polyurethane resin, and at the same time, to form the polyurethane molding having excellent heat resistance. It is to provide a method of obtaining things.

[0007]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, have found that the thermal oxidation of a polyurethane resin, especially a polyether-based polyurethane resin, at high temperature assuming thermoforming is performed. Focusing on suppression, it was found that stabilization of modified molding can be obtained by adding a specific antioxidant, and the present invention has been completed. That is, in the present invention, when a thermoplastic polyurethane resin is thermoformed, a specific hindered phenolic compound represented by the following general formula (1) is added to the polyisocyanate compound. (In the formula, R represents a t-butyl group.)
It is a method for modifying and molding a polyurethane resin, which comprises molding after adding and mixing the polyisocyanate compound added with 0.05 to 2.0 parts by weight.

Regarding the heat resistance of the polyurethane resin, especially the polyether polyurethane is greatly deteriorated by heat.
This is because the ether bond is susceptible to thermal oxidation. This thermal oxidation is considered to proceed according to the mechanism shown in chemical formula (I).

Therefore, in thermoforming, it can be easily estimated that the above reaction is occurring to some extent. Then, in the thermoforming machine in which the polyisocyanate compound is added and mixed, the reaction of the isocyanate group is involved, so that the reaction proceeds in a complicated manner, and as a result, a three-dimensional reticulated non-melted material is generated. Furthermore, this behavior becomes even more pronounced when the polyisocyanate compound is modified with a polyether polyol.

The use of various antioxidants to prevent the oxidative degradation is well known. However, many of these antioxidants are added at the time of synthesizing the thermoplastic polyurethane resin or at the time of pelletizing, and thus receive a thermal history, and the antioxidant effect is lowered at the time of thermoforming. Therefore, in the reforming molding involving the addition and mixing of the polyisocyanate compound, in order to stabilize the molding and obtain a molded product having excellent heat resistance,
Maintaining the antioxidant effect is important.

That is, by adding and mixing the specific hindered phenolic compound represented by the general formula (1) to the polyisocyanate compound used as the modifier and subjecting it to the reforming molding, excellent molding stability and A molded article having excellent heat resistance could be obtained.

Next, the addition of the hindered phenol compound to the polyisocyanate compound is far less subject to heat history than the addition to the thermoplastic polyurethane resin, and the antioxidant of the hindered phenol compound is prevented. It is effective for maintaining the effect. From the viewpoint of thermal history, there is also a method of adding to the thermoplastic polyurethane resin immediately before use and dry blending, but with this method, quick compatibility with the polyurethane resin in the molding machine cannot be expected, and its effect can not be expected. Can not. Furthermore, it goes without saying that the addition of the hindered phenol to the polyisocyanate compound effectively acts on the heat resistance stabilization of the polyisocyanate compound itself. Especially when the polyisocyanate compound is modified with a polyether polyol, the effect is further exhibited.

There are various methods for adding the hindered phenol compound represented by the general formula (1) of the present invention to the polyisocyanate compound. It may be added at the initial stage of polyisocyanate production, or conversely at the final stage. Further, it may be added just before the polyisocyanate compound is supplied to the molding machine. In any case, it is necessary that the hindered phenol compound is uniformly dispersed in the polyisocyanate compound. Any known method can be applied as the mixing method, but it is not preferable to give a heat history more than necessary when mixing.

The amount of the hindered phenol compound represented by the general formula (1) in the present invention added to the polyisocyanate compound is 0.05 to 2.0 parts by weight based on 100 parts by weight of the polyisocyanate compound. If the amount is less than 0.05 parts by weight, there is almost no effect, and if the amount is more than 2.0 parts by weight, the effect is not improved. The preferable addition amount is 0.1 to 1.0 part by weight.

The polyisocyanate compound used in the present invention is diphenylmethane diisocyanate (hereinafter referred to as MDI).
Abbreviated) and a polyether polyol having a molecular weight of 60 to 5,000, and having a molecular weight of 300 to 6000,
A prepolymer having an NCO content of 2 to 29% by weight is preferable.

As the polyether polyol for obtaining the polyisocyanate compound, water, polyhydric alcohol, polyhydric phenol, alkanolamine, mono- or polyamine and the like are used as an initiator, and cyclic ethers are addition-polymerized. is there. The number of functional groups of this polyether polyol is preferably 2 to 8, more preferably 2 to 3.

As the polyhydric alcohol as the initiator,
Ethylene glycol, propylene glycol, diethylene glycol, glycerin, trimethylolpropane,
Examples include hexanetriol, diglycerin, pentaerythritol, methylglycoxide, dextrol, sorbitol, sucrose and the like. Examples of the polyhydric phenol as an initiator include phenol-aldehyde initial condensate, bisphenol A, bisphenol F and the like.

Examples of the alkanolamine as the initiator include monoethanolamine, diethanolamine, triethanolamine and diisopropylamine, and examples of the mono- or polyamine include aniline, diaminodiphenylmethane, tolylenediamine and ethylenediamine.

Examples of cyclic ethers include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin and halogen-substituted compounds thereof.

Further, there is poly (oxytetramethylene) glycol (hereinafter abbreviated as PTMG) obtained by ring-opening polymerization of tetrahydrofuran, and the preferred polyether polyol is PTMG.

[0021]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. In the text, "part" means "part by weight". Further, the present invention is not limited to these examples.

Preparation of Polyisocyanate Compound (1) Polyisocyanate Compound A 170 parts of PTMG having a molecular weight of 850 and 100 parts of MDI are reacted at 80 ° C. for 3 hours to give a polyisocyanate compound having an isocyanate group of less than 6.2% NCO content. An isocyanate compound was prepared. (2) Polyisocyanate Compound B To 100 parts of polyisocyanate compound A, 0.3 part of Irganox 1010 (manufactured by Ciba-Geigy, a compound represented by the general formula (1), hereinafter abbreviated as I-1010) was added, and the mixture was heated at 80 ° C. And mixed with stirring for 1 hour. (3) Polyisocyanate compound C With respect to 100 parts of polyisocyanate compound A, I-1
It was prepared in the same manner as the polyisocyanate compound B by adding 0.5 part of 010. (4) Polyisocyanate compound D With respect to 100 parts of polyisocyanate compound A, I-1
It was prepared in the same manner as the polyisocyanate compound B by adding 1.0 part of 010. (5) Polyisocyanate compound E 0.5 part of Yoshinox BHT (manufactured by Yoshitomi Pharmaceutical Co., Ltd., hindered phenolic compound, hereinafter abbreviated as BHT) was added to 100 parts of polyisocyanate compound A, and the same method as for polyisocyanate compound B was performed. It was prepared in.

(6) Polyisocyanate compound F To 100 parts of polyisocyanate compound A, 0.5 part of Irganox 1035 (hindered phenol compound manufactured by Ciba-Geigy, hereinafter abbreviated as I-1035) is added to give polyisocyanate compound A. Prepared in the same way as B. (7) Polyisocyanate compound G To 100 parts of polyisocyanate compound A, 0.5 part of Irganox 1076 (manufactured by Ciba-Geigy, hindered phenol compound, hereinafter abbreviated as I-1076) was added to give polyisocyanate compound B. Prepared in the same way. (8) Polyisocyanate compound H To 100 parts of polyisocyanate compound A, 0.5 part of Irganox 1098 (manufactured by Ciba-Geigy, hindered phenol compound, hereinafter abbreviated as I-1098) is added to give polyisocyanate compound B. Prepared in the same way. (9) Polyisocyanate compound I To 100 parts of polyisocyanate compound A, 0.5 part of Irganox 245 (manufactured by Ciba-Geigy, hindered phenol compound, hereinafter abbreviated as I-245) is added to give polyisocyanate compound B. Prepared in the same way.

(10) Polyisocyanate Compound J 143 parts of PTMG having a molecular weight of 650 and 100 parts of MDI were reacted at 80 ° C. for 3 hours to prepare a polyisocyanate compound having an isocyanate group with an NCO content of less than 6.2%. . (11) Polyisocyanate compound K With respect to 100 parts of polyisocyanate compound J, I-1
0.3 part of 010 was added and mixed with stirring at 60 ° C. for 1 hour. (12) Polyisocyanate compound L With respect to 100 parts of polyisocyanate compound J, I-1
It was prepared in the same manner as the polyisocyanate compound K by adding 1.0 part of 010.

(13) Polyisocyanate compound M 150 parts of PTMG having a molecular weight of 2000 and MDI 100
And 3 parts at 80 ° C. for 3 hours to give an NCO content of 10.9
A polyisocyanate compound having less than 10% of isocyanate groups was prepared. (14) Polyisocyanate compound N With respect to 100 parts of polyisocyanate compound M, I-1
0.3 part of 010 was added and mixed with stirring at 70 ° C. for 1 hour. (15) Polyisocyanate compound P With respect to 100 parts of polyisocyanate compound A, I-1
It was prepared in the same manner as the polyisocyanate compound N by adding 1.0 part of 010.

Example 1 60 g of N-4330 (manufactured by Nippon Polyurethane Industry Co., Ltd., a polyether-based thermoplastic polyurethane resin, hardness: 83 ° A) was added to a mixing tank of a Labo Plastomill (manufactured by Toyo Seiki Co., Ltd.) prepared at 200 ° C in advance. The mixture was charged and kneaded at a rotation speed of 60 rpm for 2 minutes. Then, 9 g of polyisocyanate compound B prepared at 80 ° C. was added, and the mixture was kneaded at the same rotation speed for 9 hours. During this period, changes in torque during kneading were tracked to obtain the maximum torque value (see FIG. 1). After 9 hours, the kneaded sample was compression-molded into a sheet having a thickness of 2 mm, subjected to a dynamic viscoelasticity measuring device (manufactured by Orientec), and the storage elastic modulus (E ') was measured at 110 Hz to determine the pour point. It was determined (see FIG. 2). The results are shown in Table 1.

Example 2 The same procedure and operation as in Example 1 were carried out using polyisocyanate compound C as the polyisocyanate compound. The results are shown in Table 1.

Comparative Example 1 The same procedure and operation as in Example 1 were carried out using polyisocyanate compound A as the polyisocyanate compound. The results are shown in Table 1.

Example 3 60 g of P390 (manufactured by Nippon Polyurethane Industry Co., Ltd., polyether-based thermoplastic polyurethane resin, hardness 90 ° A) was charged in a mixing tank of Labo Plastomill (manufactured by Toyo Seiki) adjusted to 205 ° C. in advance. The mixture was kneaded at a rotation speed of 60 rpm for 2 minutes. Then, 12 g of polyisocyanate compound C adjusted to 80 ° C. was added, and the mixture was kneaded at the same rotation speed for 9 hours.
During this time, the change in torque during kneading was traced to obtain the maximum torque value. After 9 hours, the kneaded sample was compression-molded into a sheet having a thickness of 2 mm, subjected to a dynamic viscoelasticity measuring device (manufactured by Orientec), and the storage elastic modulus (E ') was measured at 110 Hz to determine the pour point. I asked. The results are shown in Table 1.

Comparative Example 2 The same procedure and operation as in Example 3 were carried out using polyisocyanate compound A as the polyisocyanate compound. The results are shown in Table 1.

Example 4 P395 (manufactured by Nippon Polyurethane Industry Co., Ltd., polyether-based thermoplastic polyurethane resin, hardness 9) was placed in a mixing tank of Labo Plastomill (manufactured by Toyo Seiki) adjusted to 210 ° C. in advance.
60g of 5 ° A) was charged and kneaded for 2 minutes at a rotation speed of 60 rpm. Then, 14 g of polyisocyanate compound D adjusted to 80 ° C. was added, and the mixture was kneaded at the same rotation speed for 9 hours.
During this time, the change in torque during kneading was traced to obtain the maximum torque value. After 9 hours, the kneaded sample was compression-molded into a sheet having a thickness of 2 mm, subjected to a dynamic viscoelasticity measuring device (manufactured by Orientec), and the storage elastic modulus (E ') was measured at 110 Hz to determine the pour point. I asked. The results are shown in Table 1.

Comparative Example 3 Polyisocyanate compound A was used as the polyisocyanate compound in the same manner and operation as in Example 4. The results are shown in Table 2.

Comparative Example 4 Polyisocyanate compound E was used as the polyisocyanate compound in the same manner and operation as in Example 1. The results are shown in Table 2. Comparative Example 5 The same procedure and operation as in Example 1 were carried out using polyisocyanate compound F as the polyisocyanate compound. The results are shown in Table 2. Comparative Example 6 Polyisocyanate compound G was used as the polyisocyanate compound in the same manner and operation as in Example 1. The results are shown in Table 2.

Comparative Example 7 Polyisocyanate compound H was used as the polyisocyanate compound in the same manner and operation as in Example 1. The results are shown in Table 2. Comparative Example 8 The same procedure and operation as in Example 1 were carried out using polyisocyanate compound I as the polyisocyanate compound. The results are shown in Table 2.

Example 5 A static kneading machine having 10 elements directly connected to a belt die was arranged at the tip of a single-screw extruder having a screw diameter of 45 mm and L / D = 25, and P390 (manufactured by Nippon Polyurethane Industry Co., Ltd., Polyether thermoplastic polyurethane resin,
Hardness 90 ° A) was supplied from a hopper with a constant amount feeder, while polyisocyanate compound C adjusted to 80 ° C
To a static kneading machine via a metering pump, P390 1
Molten P3 by supplying 20 parts to 00 parts
While kneading 90 and the polyisocyanate compound C, a belt having a thickness of 2 mm was continuously formed. It was possible to perform molding without any problem for 8 hours from the start of molding, and no foreign matter was found on the belt.

Comparative Example 9 Using the same method and apparatus as in Example 5, but using polyisocyanate compound A as the polyisocyanate compound, P3
90 belts were formed, but from 2.5 hours after the start of forming, the discharge was observed to fluctuate, and foreign matter was recognized on the belt surface and inside. Therefore, the operation was stopped in 3.5 hours.

Example 6 Polyisocyanate compound K was used as the polyisocyanate compound in the same manner and operation as in Example 1. The results are shown in Table 3.

Example 7 A polyisocyanate compound L was used as the polyisocyanate compound in the same manner and operation as in Example 6. The results are shown in Table 3.

Comparative Example 10 Polyisocyanate compound J was used as the polyisocyanate compound in the same manner and operation as in Example 6. The results are shown in Table 3.

Example 8 Polyisocyanate compound N was used as the polyisocyanate compound in the same manner and operation as in Example 3. The results are shown in Table 3.

Example 9 Polyisocyanate compound P was used as the polyisocyanate compound in the same manner and operation as in Example 8. The results are shown in Table 3.

Comparative Example 11 Polyisocyanate compound M was used as the polyisocyanate compound in the same manner and operation as in Example 8. The results are shown in Table 3.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

As described above, the present invention is based on the addition and mixing of the thermoplastic polyurethane resin with the polyisocyanate compound. In the modified molding, it is possible to provide a polyurethane molded product having stable moldability and excellent heat resistance, which is industrially very useful. In particular, it can be effectively used in the production of polyurethane elastic yarn, which requires stable production of a yarn that requires heat resistance for a long time.

[Brief description of drawings]

FIG. 1 is a torque change in kneading a thermoplastic polyurethane resin and a polyisocyanate compound. The lower the maximum torque, the more stable the moldability.

FIG. 2 shows the heat resistance as the storage elastic modulus (E ′) of a sample after kneading a thermoplastic polyurethane resin and a polyisocyanate compound changes with temperature and the pour point increases.

Claims (2)

[Claims] 1. When thermoforming a thermoplastic polyurethane resin, the polyisocyanate compound has the following general formula (1):
Specific hindered phenolic compound represented by (In the formula, R represents a t-butyl group.)
A method for modifying and molding a polyurethane resin, which comprises molding after adding and mixing the polyisocyanate compound to which 0.05 to 2.0 parts by weight has been added. 2. The polyisocyanate compound is a prepolymer obtained by reacting a polyether polyol having a molecular weight of 60 to 5000 with diphenyl methane diisocyanate, having a molecular weight of 300 to 6000 and an NCO content of 2 The method for modifying and molding a thermoplastic polyurethane resin according to claim 1, wherein the amount is from 29 to 29% by weight.