JPH0368048B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a urethane resin composition having excellent heat resistance and moist heat resistance, a molded article obtained by curing this composition, and a belt. (Prior Art) Polyurethane is produced by using high-molecular polyol and polyisocyanate as raw materials and curing them with a curing agent or a low-molecular compound having two or more active hydrogen atoms in the molecule, called a curing agent or a chain extending chain. Among polyurethane elastomers, castable urethane elastomers have excellent mechanical properties, abrasion resistance, oil resistance, etc., so they have been widely used for belts, rollers, various molded objects, sheets, etc. . (Problems to be Solved by the Invention) However, the urethane elastomers produced by these conventional techniques cannot be said to have sufficient properties such as heat resistance and moist heat resistance. When performing an elastic test,
Conventional urethane resin compositions (for example, Takenate L-
2705: The softening point of the urethane elastomer obtained by curing urethane elastomer made of tolylene diisocyanate and polytetramethylene ether glycol (manufactured by Takeda Pharmaceutical Company, Ltd.) had a limit of 180 to 200°C. Therefore, flat belts,
When manufacturing belts such as V-belts and toothed belts, especially when the belt is used under high loads and high-speed operation, the temperature of the belt itself increases and physical properties deteriorate, and urethane belts cannot be used at room temperature. However, it is currently not used in high temperature ranges. In addition, conventional urethane elastomers are sensitive to temperature changes, and their hardness and elasticity decrease as the temperature rises, which has the disadvantage that the running time of the belt is significantly shortened.
Since the belt does not have sufficient heat and humidity resistance, it easily undergoes hydrolysis in a high temperature and humidity environment, and as a result, various physical properties deteriorate and the belt cannot function satisfactorily. The present invention is intended to solve the above-mentioned drawbacks, and its purpose is to provide a urethane resin composition capable of obtaining a belt with significantly improved heat resistance and moist heat resistance, and a product obtained by curing the composition. Our objective is to provide molded products and belts. (Means for Solving the Problems) The urethane resin composition according to the present invention comprises trans-cyclohexane-1,4-diisocyanate and polytetramethylene ether glycol having an average molecular weight of 1000 to 2000 in a molar ratio of NCO/OH. but
Urethane prepolymer obtained by blending in the range of 1.8 to 2.2, (A) diethyltoluenediamine, and (B)
3,3'-dichloro-4,4'-diaminodiphenylmethane in an equivalent ratio of (A)/(B) = 1/8 to 1/2
It has a mixed curing agent blended in the ratio of
This achieves the above objective. Furthermore, the molded article of the present invention is obtained by curing the urethane resin composition, thereby achieving the above object. Further, in the belt of the present invention, the molded product is one selected from the group consisting of a flat belt, a toothed belt, and a V-belt, thereby achieving the above object. The polytetramethylene ether glycol (PTMEG) used in the present invention has an average molecular weight in the range of 1000 to 2000.
When the average molecular weight of PTMEG exceeds 2000, the viscosity of the resulting urethane prepolymer becomes too high when melted, resulting in poor workability, and when the average molecular weight of PTMEG is less than 1000, the hardness of the resulting urethane elastomer becomes high. Too much. That is, when producing a belt with a urethane resin composition, the hardness of the belt is preferably in the range of about 80 to 95 according to JIS A, and by using PTMEG with the above molecular weight, urethane with a hardness suitable for the belt can be obtained. An elastomer is obtained. Further, the above-mentioned PTMEG and trans-cyclohexane-1,4-diisocyanate (t-CHDI) are mixed at a molar ratio of NCO/OH in the range of 1.8 to 2.2 to obtain a urethane prepolymer. If the NCO/OH molar ratio is outside the above range, the hardness of the urethane elastomer obtained by curing will be outside the JIS A value of approximately 80 to 95, making it suitable for use as a belt. Not. The urethane prepolymer thus obtained is chain-extended with a curing agent to produce a polyurethane elastomer. At this time, the curing agent used is the following compound containing two or more active hydrogen-containing groups in the molecule. . That is, (A) diethyltoluenediamine and (B)
A mixed curing agent of 3,3'-dichloro-4,4'-diaminodiphenylmethane (also known as 4,4'-methylene-bis(2-chloroaniline) or MOCA) is used. These mixed curing agents have an equivalent ratio of amino groups (-NH ₂ ) contained in the molecule.
(A)/(B) is used at a ratio of 1/8 to 1/2, and by using a mixed curing agent in this range, the pot life of the urethane resin composition (urethane prepolymer improves fluidity) It is possible to obtain a urethane elastomer that has a suitable workability (workable time), good workability, and well-balanced physical properties. If the curing agent is diethyltoluenediamine or 3,3'-dichloro-4,4'-diaminodiphenylmethane alone, the pot life of the composition will be inadequate and workability will suffer, making it impractical. For example, when the curing agent is diethyltoluenediamine alone, the pot life is as short as several tens of seconds, and when the above-mentioned urethane prepolymer and curing agent are mixed, the viscosity of the polyurethane resin composition increases within several tens of seconds, making casting difficult. It becomes difficult. On the other hand, the curing agent is 3,3′-
When dichloro-4,4'-diaminodiphenylmethane is used alone, the pot life of the composition is too long, 40 minutes or more, resulting in poor workability and low tensile strength of the polyurethane elastomer. The amount of the mixed curing agent mixed with the urethane prepolymer is preferably _NH2 /NCO=0.8 to 1.0. If the amount of the curing agent used is less than the above range, the tear strength of the cured product of the composition will be low, and if it exceeds the above range, the permanent elongation of the cured product of the composition will be high. Additives such as fillers, colorants, solvents, plasticizers, anti-aging agents, and stabilizers may be added to the urethane resin composition thus obtained. A molded product is obtained by pouring this composition into a mold prepared according to the purpose, heating and pressurizing it, and this molded product can be used for flat belts, toothed belts,
Used as belts, etc. (Examples) The present invention will be described in detail below based on Examples. Examples 1, 2 and Comparative Examples 1 to 4 Trans-cyclohexane-1,4-diisocyanate (t-CHDI) in the amount shown in Table 1 was added to 100 parts by weight of polytetramethylene ether glycol (PTMEG) with the molecular weight shown in Table 1. was added and reacted under a nitrogen stream at 105°C for 3 hours with stirring to obtain a urethane prepolymer having terminal isocyanate groups. Next, 100 parts by weight of the obtained urethane prepolymer was added with (A) diethyltoluenediamine and melted.
(B) 3,3'-dichloro-4,4'-diaminodiphenylmethane was blended so that the molar ratio of NH ₂ /NCO was 0.9, and this composition was heated to 110°C. Pour into mold and harden at 110°C for 10 hours.
A sheet-like molded product was obtained. Table 1 shows the evaluation of the hardness of the molded product.

[Table] Example 3 16 parts by weight of trans-cyclohexane-1,4-diisocyanate was added to 100 parts by weight of polytetramethylene ether glycol having an average molecular weight of 2000, and the mixture was reacted with stirring at 105°C for 3 hours under a nitrogen stream. A urethane prepolymer was obtained (4.25 NCO weight %, viscosity 1680 cps/80°C). Next, diethyltoluenediamine was added to the obtained urethane prepolymer as a curing agent, and 3,
9.3 parts by weight of a mixed curing agent (equivalent ratio: 1:2) with 3'-dichloro-4,4'-diaminodiphenylmethane was mixed and reacted, and the resulting urethane resin composition was heated to 110°C. Pour into belt mold,
After heating for several hours, remove from the mold and then
A flat belt was obtained by secondary curing with heated air at 110°C for 10 hours. Figure 1 shows cylindrical mold 1 used for manufacturing flat belts.
shows. The mold 1 includes an outer cylinder 12 and an inner cylinder 11, and is connected to a reactor 18 that communicates with a space 13 formed between the outer cylinder 12 and the inner cylinder 11.
A deaeration port 15 is provided at the upper end of the cylindrical space 13.
A deaeration valve 16 is removably attached to the deaeration port 15. To specifically explain the method for producing a flat belt using the mold 1, first, the degassing valve 16 of the mold 1 is opened, and a mixture of urethane prepolymer and curing agent (urethane resin composition) is poured into the reactor 18. Inlet 1
4 into the space 13 of the mold 1 or under pressure. When a small amount of the composition leaks from the degassing port 15, the degassing valve 16 is closed and the lid 18a of the reactor 18 is closed.
By pressing , a pressure higher than that during injection is further applied to the injection port 14, and in this state, the composition is cured at a predetermined temperature and under a predetermined pressure. After that, the outer cylinder 12
The cylindrical molded product is removed from the space 13 of the mold 1, and the cylindrical molded product is cut into rings in the circumferential direction to obtain a belt having an appropriate width. Note that by changing the shape of the space 13 of the mold 1, a V-belt or a toothed belt can be manufactured. To manufacture the toothed belt, the mold shown in FIG. 2 is used, and otherwise the same apparatus as shown in FIG. 1 can be used. In the mold shown in FIG. 2, a plurality of protrusions 111 are provided on the outer peripheral surface of the inner cylinder 11 parallel to the mold axis direction, and the tensile member
2 is wound around the outer periphery of this protrusion 111 in the circumferential direction. As the tensile member 112, for example, a rope-like material such as a synthetic fiber rope, a steel wire, a glass fiber rope, or a woven material is used. Next, the composition was injected into the cylindrical space 13 in the same manner as in Example 3, and then molded and cured, and the grooved cylindrical cured product was taken out and cut into rings with a width of 6.4 mm. Toothed belt A (number of teeth) shown in Fig. 5
50). The dimensions of this toothed belt A are as follows:
In the figure, a is 2.30mm, b is 1.27mm, and c is 0.25mm.
mm and d are 2.57 mm, and θ is 50°. Next, the toothed belt thus obtained was subjected to an overload durability test. When running tests were conducted on the toothed belt under the conditions of a rotation speed of 6500 rpm and a load of 0.368 Kw, no abnormalities were observed even after running for 500 hours. Example 4 Diethyltoluenediamine as a curing agent,
A flat belt was obtained in the same manner as in Example 3, except that 1000 parts by weight of a mixed curing agent with 3,3'-dichloro-4,4'-diaminodiphenylmethane (1:8 in equivalent ratio) was used. . Comparative Example 5 Diethyltoluenediamine 7.0 as curing agent
A flat belt was produced in the same manner as in Example 3 except that only parts by weight were used, but in this case the pot life was so short as several tens of seconds that casting could not be performed. Comparative Example 6 A flat belt was obtained in the same manner as in Example 3, except that only 10.4 parts by weight of 3,3'-dichloro-4,4'-diaminodiphenylmethane was used as the curing agent.
In this case, the pot life was long, about 1 hour, and workability was extremely poor. Comparative Example 7 As a curing agent, 3.4 parts by weight of 1,4-cyclohexanedimethanol and 1.5 parts by weight of trimethylolpropane
A flat belt was obtained in the same manner as in Example 3, except that 0.01 part by weight of tin octylate was used as the catalyst. Comparative Example 8 As a commonly used urethane prepolymer, Takenate L-2705 (manufactured by Takeda Pharmaceutical Co., Ltd., consisting of tolylene diisocyanate and polytetramethylene ether glycol, with an isocyanate content of
2.80%) 100 parts by weight, 3 as curing agent,
A flat belt was obtained in the same manner as in Example 3, except that 8.0 parts by weight of 3'-dichloro-4,4'-diaminodiphenylmethane was used. Table 2 shows the physical properties of the flat belt obtained as described above.

[Table] As shown in Examples 3 and 4, two types of curing agents were used: (A) diethyltoluenediamine and (B) 3,3'-dichloro-4,4'-diaminodiphenylmethane, And the equivalent ratio of the curing agent is (A)/(B) = 1/8 ~
By setting the ratio to 1/2, a polyurethane elastomer exhibiting superior tensile strength (Tb) compared to Comparative Examples 6 and 7 was obtained. Next, changes over time in the heat resistance and moist heat resistance of the belts produced using the compositions obtained in Example 3 and Comparative Examples 7 and 8 were measured. In the heat resistance test, the samples were stored at a temperature of 100°C, and changes in breaking strength over time were investigated at the initial stage, after 28 days, and after 56 days. Moisture and heat resistance was determined by measuring changes over time when the sample was stored at a temperature of 70° C. and a relative humidity of 95% in the same manner as above. The results are shown in Tables 3 and 4.

【table】

[Table] As shown in Tables 3 and 4, in Comparative Examples 7 and 8, the breaking strength after 56 days was significantly inferior, and the heat resistance and moist heat resistance were significantly inferior, but Example 3
No decrease in strength occurred. Next, as an evaluation of heat resistance, a viscoelasticity test (Resca; viscoelasticity measuring device RD-1100AD) was conducted on the molded products of the compositions of Example 3 and Comparative Examples 7 and 8. The results are shown in Figure 6. As shown in Figure 6, the softening point of conventional polyurethane elastomers is limited to around 200°C and it is difficult to exceed 250°C, but the softening point of the molded product of Example 3 is around 300°C. It was confirmed that the heat resistance was improved. (Effect of the invention) As described above, the molded product obtained by curing the composition of the present invention has a softening point of 250°C or higher, heat resistance,
It has excellent heat and humidity resistance and can be suitably used as a composition for belts used in high loading and high speed operations. Moreover, the above composition has an appropriate pot life and is excellent in workability in the molding and curing process. The various belts produced in this way have excellent heat resistance and heat and humidity resistance, have a long running time, and do not deteriorate in physical properties even under high temperature and high humidity environments.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a molding die according to an embodiment of the present invention;
Fig. 2 is a cross-sectional view of the main parts of a mold for manufacturing a toothed belt, Fig. 3 is a partially cutaway perspective view of the toothed belt, Fig. 4 is a partially cutaway side view of the toothed belt, and Fig. 5 is a partially cutaway side view of the toothed belt. FIG. 4 is a sectional view taken along the line V-V, and FIG. 6 is a graph showing the relationship between temperature and rigidity of the urethane elastomer. 1... Mold, 11... Inner cylinder, 12... Outer cylinder, 1
3...Space part.

Claims (1)

[Scope of Claims] 1 Trans-cyclohexane-1,4-diisocyanate and polytetramethylene ether glycol having an average molecular weight of 1000 to 2000 are combined in NCO/OH
A urethane prepolymer obtained by blending in a molar ratio of 1.8 to 2.2, (A) diethyltoluenediamine, and (B) 3,3'-dichloro-4,4'-diaminodiphenylmethane, A urethane resin composition having a mixed curing agent blended in an equivalent ratio of (A)/(B) = 1/8 to 1/2 is cured, and the hardness is the value of JlS A. 80 at
Belt that is ~95.