JPH041007B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to urethane elastomers with improved heat resistance. There are two types of urethane elastomers: thermosetting elastomers, such as adiprene, and thermoplastic elastomers.The former is mainly used in industrial products, while the latter is used in solutions, such as in leather coatings and adhesives. There is. Conventional thermosetting elastomers are made of long-chain polyols such as polytetramethylene glycol (PTMG) and polyethylene adipate (PEA), and polyisocyanates such as tolylene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI). A prepolymer having terminal isocyanate (NCO) groups is synthesized by reacting with
This is one component, and other components include diamines represented by 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), ethylene glycol (EG), and 1,4-butanediol (1, Using a diol such as 4-BG), stir and mix these two components in a casting machine, and after casting into a specified mold,
After being heated for a long time at a temperature of around 100℃ (called post-curing), the product is removed from the mold. The above-mentioned conventional thermosetting urethane elastomers have good wear resistance, but have the drawback of low heat resistance. For example, rolls for steel have problems when used at temperatures above 100°C, and even anti-vibration materials are limited to use when the surface temperature is below 120°C.
Furthermore, in terms of molding, it has the disadvantage that the molding time is significantly longer than that of thermoplastic urethane, RIM (Reaction Injection Molding) urethane, etc., and it requires a long post-cure after casting, which results in poor mold rotation rate. There is a drawback. An object of the present invention is to provide a thermosetting urethane elastomer having extremely excellent heat resistance. The purpose of the present invention is to shorten the molding time by heat-treating at high temperature and in a short time without requiring the conventional long-time post-cure, and to produce a thermosetting urethane elastomer obtained by a method with a high mold rotation rate. It is about providing. The urethane elastomer with improved heat resistance of the present invention is a polyisocyanate compound, a polyol () having an average molecular weight of 500 to 5000 and having two or more active hydrogen groups, and a general formula (A) _n (---CH ₂ OH). _o
[In the formula, A represents an aliphatic ring, an aromatic ring, or a heterocycle, m represents an integer of 1 or more, and n represents an integer of 2 or more] Each component of the polyol () having at least two terminal hydroxyl groups After reacting and curing a composition for producing polyurethane stoichiometrically blended under conditions where the equivalent ratio of ()/() of polyol () and polyol () is 1.5 or more, the resulting polyurethane is cured at a temperature exceeding 180°C. Obtained by heat treatment at temperature. Various types of polyisocyanate compounds can be used as the polyisocyanate compound used in the present invention, but among them, polyisocyanates having an aromatic ring are preferred, such as TDI, MDI, xylylene diisocyanate (XDI), toluidine diisocyanate (TODI),
Suitable examples include naphthylene diisocyanate (NDI), polyalkylene polyphenyl isocyanate (PAPI), and carbodiimidated polyisocyanates thereof. Also usable are isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), hydrogenated MDI, hydrogenated TDI, and the like. The polyol () used in the present invention is a polyol having an average molecular weight of 500 to 5000 and having two or more active hydrogen groups, and various polyether polyols, polyester polyols, polycarbonate polyols, etc. can be used. Among polyether polyols, poly(oxytetramethylene) glycol is preferred, and among polyester polyols, polyethylene adipate polyol,
Polybutylene adipate polyol, poly-ε-
Caprolactone polyol is preferred, and among polycarbonate polyols, polybutylene carbonate polyol and polyhexamethylene carbonate polyol are preferred. The polyol () used in the present invention has the general formula (A) _n (---CH ₂ OH) _o [where A is an aliphatic ring, aromatic ring, or heterocycle, m is an integer of 1 or more, and n is 2 It is a polyol having at least two terminal hydroxyl groups represented by the following integer: In the above, the aliphatic ring is, for example, a cycloalkane ring having 5 to 8 carbon atoms, and the aromatic ring is a benzene ring.
naphthalene ring or formula

[Formula] (In the formula, B is O, S, -SO ₂ -, -CH ₂ -, -C
(CH ₃ ) ₂ −,

Examples of polynuclear aromatic rings and heterocycles represented by [Formula] (indicates others) include:

[Formula] etc. can be mentioned. m is an integer greater than or equal to 1, and the preferred range is 1.
-5, while n is an integer of 2 or more, with a preferable range of 2-5. Preferred specific examples of polyols include 1 and 2
- (or 1,3- or 1,4-) cyclohexanedimethanol (CHDM), 1,2- (or 1,3- or 1,4-) xylylene diol (XD), 1,8-naphthalenedimethanol ,
2,2-bis(p-hydroxymethylphenyl)
Propane, bis(p-hydroxymethylphenyl) sulfone, bis(p-hydroxymethylphenyl)ether, bis(p-hydroxymethylphenyl)thioether, β-hydroxyethyl terephthalate (BHET), β, β, β′ , β'-tetramethyl-2,4,8,10-tetraoxaspiro-(5,5)-undecane-3,9-diethanol, β,β-dimethyl-β',β'diphenyl-2,
Examples include 4,8,10-tetraoxaspiro-(5,5)-undecane-3,9-diethanol. In the present invention, each of the above components is mixed under conditions where the equivalent ratio of polyol () to polyol () is 1.5 or more.
A urethane elastomer with significantly improved heat resistance can be obtained by stoichiometrically blending a polyisocyanate component and a polyol component, reaction-curing the resulting polyurethane, and then heat-treating the resulting polyurethane at a temperature above T ₁ . Here, the above-mentioned stoichiometric means, for example, that the equivalent ratio of NCO/active hydrogen is approximately 0.95.
This means blending within a range of ~1.15. In the present invention, catalysts, blowing agents, reinforcing agents, pigments, and others may be added as necessary. Reaction and curing may be carried out by conventional methods. The polymer structure of the urethane elastomer of the present invention is a so-called blocked urethane elastomer having repeating units of polyol () and polyisocyanate, and segments each consisting of polyol () and polyisocyanate, and the equivalent ratio of polyol () and polyol () is is 1.5 or more. The method for synthesizing the blocked urethane elastomer of the present invention may be any of the prepolymer method, one shot method, and other methods. In the case of a high melting point compound among polyols () with a melting point of 100℃ or higher, dissolve it in a solvent in advance, add an excess of the polyisocyanate compound, and dissolve the terminal NCO.
A useful method is to react to form a base and then distill off the solvent to obtain a mixed polyisocyanate composition with a lower melting point. In the present invention, the desired highly heat-resistant urethane elastomer can be obtained by reaction-curing the polyisocyanate and polyol components and then heat-treating the resulting polyurethane at a temperature exceeding 180°C without performing any post-curing. However, of course, there is no problem in using post cure together. The reason why the urethane elastomer of the present invention exhibits excellent heat resistance is thought to be due to the synergistic effect of its polymer structure and the means of heat treatment at temperatures exceeding 180°C. That is, it is considered that the thermal stability of the hard segment block composed of repeating units of polyol () and polyisocyanate in the blocked urethane elastomer of the present invention greatly contributes to the heat resistance of the elastomer. For example, one method for evaluating heat deterioration resistance is to expose a predetermined test piece to an air atmosphere at a constant temperature for a long period of time, then check for changes in appearance and measure weight loss of the test piece. In this method, PTMG-TDI prepolymer, which is generally well known as a thermosetting urethane elastomer,
Polyurethane obtained by reaction with MOCA
When urea is exposed to conditions of 160° C. x 108.5 hours, it turns black and becomes molten, but the blocked urethane elastomer of the present invention, which was measured at the same time, maintained its original shape and only slightly yellowed. Next, the temperature dependence of thermal denaturation is significantly improved by heat treating the blocked urethane elastomer of the present invention at a temperature exceeding 180°C. This heat treatment is different in technical concept from post-cure conventionally known in this field, and is extremely effective for the blocked urethane elastomer of the present invention. The urethane elastomer of the present invention can be used for various purposes, but it is particularly useful as vibration-proofing materials used in steel rolls, compressor frames, etc., which require high heat resistance. The present invention will be described in detail below with reference to Reference Examples, Examples, and Comparative Examples. The compounding materials and test methods used are as follows. (1) Polyisocyanate MDI Millionate MT (Japan Polyurethane) Takenate N2710 NCO% = 4.32 (Takeda Pharmaceutical) (2) Polyol () PTMG PTMG2000 (OHV = 57.7, Mitsubishi Kasei) PEA Nitsuporan 4040 (OVH = 56.1, Japan Polyurethane) PCG Desmofene 2020E (OVH=56, Bayer) PEAT2000 aromatic polyester polyol (OVH=124) (3) Polyol () CHDM cyclohexanedimethanol (Eastman) m-XD m-xylylene diol (Mitsubishi Gas Chemical) (4) DSC measurement method Approximately 30 mg of a sample piece was
The temperature was raised to 10°C at a rate of 10°C per minute, and the endothermic peak due to phase transition was measured. (5) Measuring method of molecular weight measurement change 0.5g of the initial sample piece or the sample piece after heat aging at 160℃ x 108.5 hours was added to di-n-butylamine/DMF.
Dissolve in 1.5 ml of a mixed solvent with a volume ratio of (0.5/1) and dilute with 10 ml of THF. Using this sample solution, molecular weight was measured by high speed gel permeation chromatography. Reference Examples 1 to 6 Polyurethane is produced by a prepolymer method using the polyisocyanate and polyol components listed in Table 1, and the polyurethane is post-cured under the usual conditions of 90°C x 16 hours.Heating loss and molecular weight of elastomers obtained The change and weight loss onset temperature were measured. Reference example 6 uses Takenate N2710 and MOCA.
The results are shown for polyurethane obtained by reaction curing under conditions where the NCO/active hydrogen equivalent ratio is 1.05. From Table 1, the loss on heating of Reference Example 6 is about 2.5 to 4 times greater than that of the blocked urethane elastomers of the present invention of Reference Examples 1 to 5 using polyol (), and the molecular weight of Reference Example 6 also decreases. So the initial 1/
In contrast, in Reference Examples 1 to 5, the ratio remained at 1/3 or more. Further, the temperature at which weight loss starts is 241°C in Reference Example 6, but it is 260°C or higher in Reference Examples 1 to 5. From these results, it is clear that the blocked urethane elastomer of the present invention has extremely excellent heat deterioration resistance.

[Table] Reference Examples 7 to 8 and Examples 1 to 2 Using the same urethane elastomer as Reference Example 3, T ₁ of this urethane was obtained without post-curing.
The heat resistance of the materials heat-treated at a temperature of 120°C or higher was evaluated by the temperature at which the endothermic peak appeared in the DSC curve. In addition, simply post-cure (90×
Table 2 also shows the results of the samples that were only treated (for 16 hours) (Comparative Example 1) and those that were heat-treated at 120° C. for 300 minutes after post-curing (Comparative Example 2). Also, Reference Examples 7-8, Examples 1-2 and Comparative Examples 1-2
Figure 1 shows the DSC curve obtained. As is clear from Figure 1, in Comparative Example 2, the transition of the blocked polyurethane started at 125°C and reached 183°C.
shows the peak. This DSC curve is almost the same as the DSC curve of Comparative Example 1 with only post-cure and no heat treatment, and does not show the effect of heat treatment. on the other hand
In Reference Examples 7 and 8 and Examples 1 and 2, in which heat treatment was performed at 150° C. or higher, the DSC endothermic peak shifted to the high temperature side. In particular, when heat treatment is performed at a temperature exceeding 180°C, almost no endotherm is observed at temperatures below 180°C.

[Table] Comparative Example 3 A polyurethane was prepared in the same manner as in Reference Example 3 except that the equivalent ratio of polyol ()/polyol () was 1, and T ₁ was 105°C. When this urethane was heat-treated at temperatures of 115℃ and 150℃, it was found that at both heat treatment temperatures,
The DSC curve remained almost unchanged, and no heat treatment effect was observed. This is because the equivalent ratio of polyol ()/polyol () is 1, and there is no formation of hard segments that would transform to a more stable crystal structure, and the blocking properties of the hard segments are _small . This is thought to be because there is little change in the polymer structure even after heat treatment. Comparative Example 4 The temperature at which the endothermic peak appears in the DSC curve was measured in the same manner as in Example 1 except that the heat treatment temperature was 140°C.184
It was warm at ℃. The DSC curve is shown in Figure 1.

[Brief explanation of drawings]

FIG. 1 is a DSC curve diagram obtained in Reference Examples 7 to 8, Examples 11 to 2, and Comparative Examples 1 to 2 and 4.

Claims (1)

[Claims] 1. Polyisocyanate compound A polyol () having an average molecular weight of 500 to 5000 and having two or more active hydrogen groups () General formula (A-) _n (CH ₂ OH) _o [In the formula, A is an aliphatic ring] , an aromatic ring or a heterocycle, m is an integer of 1 or more,
polyol () having at least two terminal hydroxyl groups represented by n is an integer of 2 or more.
A urethane elastomer with improved heat resistance obtained by heat-treating the resulting polyurethane obtained by stoichiometrically blending and reaction curing under conditions where the equivalent ratio of ()/() is 1.5 or more at a temperature exceeding 180°C.