JP2001152008A - Urethane composition for molding belt, and driving belt formed out of the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a urethane composition for molding a belt, containing a reduced amount of a mixed DOP or no DOP without damaging the characteristics of the produced belt made from a polyurethane. SOLUTION: This urethane composition for molding the belt, usable for producing the belt made from the polyurethane by casting the composition in a mold for molding the belt, and carrying out the curing reaction thereof is obtained by mixing di-(2-ethylhexyl) sebacate with a urethane prepolymer obtained by the synthesis from a polyol and a polyisocyanate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a urethane composition for forming a belt and a power transmission belt formed from the composition.

[0002]

2. Description of the Related Art In the fields of general industrial machines and office automation equipment, power transmission belts having a belt body formed of a polyurethane composition are used. Such a urethane belt is a liquid urethane prepolymer obtained by synthesizing a polyol such as polytetramethylene ether glycol and a polyisocyanate such as tolylene diisocyanate.
It is formed by injecting a urethane composition for forming a belt, into which a curing agent such as 3,3'-diaminodiphenylmethane or the like and other compounding agents have been mixed, into a casting mold and performing a curing reaction. At this time, the compounding agent contains a plasticizer, which lowers the viscosity of the urethane prepolymer to improve castability, and adjusts physical properties such as hardness and friction coefficient of the polyurethane composition constituting the belt. Will be achieved. And, as this plasticizer, di-
(2-Ethylhexyl) phthalate (hereinafter referred to as "DOP") is most commonly used.

[0003]

By the way, phthalate compounds represented by DOP are harmful chemicals called "environmental hormones" which cause genital abnormalities, neurological abnormalities and immune system abnormalities in the human body. It has been pointed out and has become a problem in recent years.

In the process of producing the urethane belt, DOP is directly handled in the step of adjusting the urethane composition. Further, since DOP does not participate in the curing reaction of the urethane prepolymer, DOP is contained in the manufactured urethane belt without changing the chemical structure,
It can bleed to the belt surface. Therefore,
D by any route by inhalation of volatile vapor or direct contact
There is a risk that OP may be absorbed and accumulated in the human body. Under such circumstances, there is a strong demand for a reduction in the amount of DOP used in urethane belts, and preferably a reduction in DOP usage.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the mixing amount of DOP as compared with the conventional one without impairing the characteristics of the produced urethane belt. An object of the present invention is to obtain an unused urethane composition for forming a belt and a power transmission belt formed from the composition.

[0006]

SUMMARY OF THE INVENTION The present invention provides di- (2-ethylhexyl) sebacate (hereinafter referred to as "DOS") which exerts a plasticizing effect on a prepolymer as a urethane composition for forming a urethane belt. It is to be mixed.

Specifically, the invention of the present application relates to a belt-forming urethane composition used for producing a urethane belt by injecting into a belt-forming mold and allowing it to undergo a curing reaction. It is characterized by mixing di- (2-ethylhexyl) sebacate with a urethane prepolymer produced by synthesizing a polyisocyanate.

According to the urethane composition for forming a belt having the above-mentioned structure, DOS is mixed as a plasticizer, so that the properties such as belt strength are not reduced as compared with the conventional one, and it is pointed out as an environmental hormone harmful to the human body. It is possible to obtain a urethane belt in which the amount of the plasticizer DOP used is reduced or the DOP is not used. Where DO
It is not clear why there is no significant difference in properties such as belt strength between the case where S is mixed and the case where DOP is mixed, but both DOP and DOS have the same degree of interaction with the polyurethane molecular skeleton. This is considered to be because there is no difference in their influence on the physical properties of the polyurethane composition.

Further, as compared with the case where a conventional DOP is used, the viscosity of the urethane composition is reduced, and the castability is improved. The reason for this is not clear, but D
It is considered that OS is superior to DOP in compatibility with the urethane prepolymer.

Further, DOS causes bleeding on the belt surface more easily than DOP, so that the friction coefficient of the belt is further reduced.

Here, the mixing amount of DOS is desirably 3 to 40 parts by weight based on 100 parts by weight of the prepolymer. If the mixing amount is less than 3 parts by weight, the effect of reducing the viscosity of the prepolymer, etc., will not be sufficiently exerted. This is because there is a risk of causing such a problem. Therefore, from such a viewpoint, the mixing amount is more preferably 10 to 30 parts by weight.

Further, a polyether glycol may be used as the polyol constituting the urethane prepolymer. In this case, since the polyether glycol has low crystallinity, the hardness of the formed polyurethane composition is sensitively affected by the amount of DOS to be mixed. Therefore, the hardness of the polyurethane composition can be easily adjusted by adjusting the amount of DOS.

Further, a polyurethane composition can be formed by mixing a polyol as a curing agent with the urethane composition and thereby performing a curing reaction. However, an amine compound is mixed as a curing agent and a curing reaction is thereby performed. To form a polyurethane urea composition. In the latter case, the reactivity of the curing reaction is high, so that the belt can be formed in a short time and the productivity can be improved.

The transmission belt formed of the urethane composition for forming a belt may be a flat belt, a V belt, a V-ribbed belt, a toothed belt, a round belt, or the like. Since the reduction is large, if you decide to form a toothed belt,
The effect of reducing noise during belt running can be obtained.

[0015]

As described above, according to the invention of the present application, since DOS is mixed as a plasticizer, characteristics such as belt strength are not reduced as compared with the conventional one, and the environment is harmful to the human body. D of plasticizer which is pointed out as a hormone
A urethane belt in which the amount of OP used is reduced or no DOP is used can be obtained. In addition, conventional D
As compared with the case where OP is used, the viscosity of the urethane composition is reduced, and the castability is improved. Further, since DOS causes bleeding on the belt surface more easily than DOP, the coefficient of friction of the belt is further reduced.

[0016]

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a toothed belt B according to an embodiment of the present invention.

The toothed belt B is formed by a belt body 1 provided with belt teeth 2, 2,... At a predetermined pitch in the belt length direction on the inner peripheral surface. A core wire 3 as a tensile member extends along the bottom of each belt tooth 2 substantially in the belt length direction and is spirally embedded with a pitch in the belt width direction. Further, a reinforcing cloth 4 is embedded so as to be located between the belt teeth 2, 2,.

The belt body 1 was obtained by synthesizing the polyol component with polytetramethylene ether glycol (hereinafter referred to as "PTMG") and the polyisocyanate component as tolylene diisocyanate (hereinafter referred to as "TDI"). 1,1′-methylenebis (o-chloroaniline) (hereinafter referred to as “MOCA”) as a curing agent, oleic acid as an organic acid as a reaction accelerator, and DOS as a plasticizer are added to a liquid urethane prepolymer. The mixed urethane composition is formed of a polyurethane urea composition that has undergone a curing reaction. Here, DOS is mixed in an amount of 3 to 40 parts by weight based on 100 parts by weight of the prepolymer.

The core wire 3 is formed of a twisted aramid fiber, and is subjected to an adhesive treatment by dipping in an epoxy resin solution and heating.

The reinforcing cloth 4 is formed of a nonwoven fabric of cellulose fibers.

Next, a method of manufacturing the toothed belt B will be described. <Reinforcing cloth / core wire setting step> The peripheral surface of an inner mold in which grooves extending in the axial direction are provided at a predetermined pitch in the circumferential direction is coated with a nonwoven fabric of cellulose fiber as a reinforcing cloth, and then made of twisted yarn of aramid fiber. The core wire is spirally wound at a predetermined pitch.

Then, the inner mold is set at the center of the cylindrical outer mold. At this time, a gap for injecting the urethane composition is formed between the inner mold and the outer mold. <Urethane composition preparation step> The temperature of the urethane prepolymer synthesized by PTMG and TDI is adjusted to 80 ° C, and the pressure is reduced to remove bubbles. Next, MOCA, oleic acid and DOS are mixed in a container controlled at 100 ° C. to form a uniform solution, which is poured into a urethane prepolymer, and stirred and mixed to form a liquid urethane composition. I do. <Urethane composition injection / curing step> The obtained urethane composition was injected into the gap between the outer die and the inner die, and this was injected into the gap for 1 hour.
Hold at 00 ° C for 60 minutes. Thereby, the curing reaction of the urethane composition is accelerated. <Demolding step> The cylindrical belt precursor is released from the outer mold and the inner mold. <Width cutting step> The removed belt precursor is cut into a predetermined width to obtain a toothed belt B.

In the toothed belt B having the above-described structure, the belt body 1 is formed of a urethane composition in which DOS is mixed as a plasticizer with a prepolymer.
Have the same properties as belt strength and the like when used. Therefore, it is not necessary to use DOP, which is pointed out as a harmful environmental hormone for the human body, as a plasticizer.

Further, since DOS causes bleeding on the belt surface more easily than DOP, the friction coefficient of the belt is further reduced, and noise during belt running is reduced.

Further, since DOS is mixed in an amount of 3 to 40 parts by weight with respect to 100 parts by weight of the urethane prepolymer, the effect of reducing the viscosity of the liquid urethane composition is sufficiently exhibited, and the bleeding to the belt surface is achieved. Will be moderate.

At the time of belt production, the conventional D
As compared with the case where OP is used, the viscosity of the urethane composition is reduced, and the castability is improved.

Further, as a polyol constituting the urethane prepolymer in the urethane composition, PT having low crystallinity may be used.
Since MG is used, the hardness of the polyurethane composition to be formed is sensitively affected by the amount of DOS mixed, and the hardness of the belt can be easily adjusted by the amount of mixing.

Furthermore, since MOCA, which is an amine compound, is mixed as a curing agent in the urethane composition, the belt body 1 formed is made of the polyurethane urea composition. In this case, since the reactivity of the curing reaction is high, the belt can be formed in a short time, and the productivity is improved. (Other Embodiments) In the above embodiment, the transmission belt formed of the urethane composition is a toothed belt. However, the present invention is not particularly limited to this, and a flat belt, a V belt,
It may be a V-ribbed belt, a round belt, or the like.

In the above embodiment, the polyol forming the urethane prepolymer of the urethane composition is P
Although TMG was used, it is not particularly limited to this, and other polyether glycols such as polypropylene ether glycol (PPG) and polyester glycols such as polyethylene adipate (PEA) and poly-ε-caprolactone glycol (PCL) It may be. However, when the crystallinity of the glycol compound is high,
Polyether glycol is preferably used because the effect of adjusting the hardness by mixing the plasticizer is small.

In the above embodiment, TDI was used as the polyisocyanate for forming the urethane prepolymer of the urethane composition. However, the present invention is not limited to this, and diphenylmethane diisocyanate (MDI)
It may be.

In the above embodiment, MOCA was used as a curing agent for the urethane composition. However, the present invention is not limited to this, and other diamine compounds and polyol compounds may be used.

In the above embodiment, oleic acid, which is an organic acid, is used as a reaction accelerator for the urethane composition. However, the present invention is not limited to this, and aliphatic carboxylic acids such as sebacic acid and adipic acid are used. The compound may be an aromatic carboxylic acid compound such as benzoic acid or toluic acid. However, oleic acid which is liquid at room temperature is particularly preferably used in consideration of workability such as compounding.

In the above embodiment, DOS is used alone as a plasticizer of the urethane composition. However, the present invention is not limited to this, and another plasticizer may be used in combination.
In that case, a combination of DOS and DOP may be used, and the effect of reducing the amount of DOS used can be obtained.

In the above embodiment, the urethane prepolymer, the curing agent, the organic acid, and the plasticizer are used. However, the present invention is not limited to this. If necessary, a pigment or a lubricant may be used. It may be a mixture.

In the above embodiment, a twisted yarn of aramid fiber is used as the core wire 3. However, the present invention is not particularly limited to this, and a twisted yarn of glass fiber or the like may be used. In addition, although a nonwoven fabric is used as the reinforcing cloth 4, a woven cloth, a knitted cloth, or the like may be used.

In the above embodiment, when the toothed belt B is manufactured, the temperature of the prepolymer is adjusted to 80 ° C., the temperature of the curing agent and the like are adjusted to 100 ° C. However, the temperature of the prepolymer is 60 to 100 ° C., the temperature of the curing agent is 100 to 150 ° C., and the temperature of the prepolymer is 100 to 150 ° C., depending on the type of the prepolymer or the curing agent. Mold temperature is 100-150
C and the heating time should be appropriately selected in the range of 10 to 90 minutes.

[0038]

EXAMPLES (Viscosity of mixture of prepolymer and plasticizer) <Test evaluation sample> -Example 1-100 parts by weight of a prepolymer having a isocyanate concentration of 5.6% and synthesized by PTMG having a molecular weight of 1,000 and TDI. On the other hand, a urethane composition containing 10 parts by weight of DOS as a plasticizer was used as Example 1. Comparative Example 1 Comparative Example 1 was the same urethane composition as in Example 1 except that DOP was mixed instead of DOS as a plasticizer. That is, it is a urethane composition according to a conventional example. Comparative Example 2 The same as Example 1 except that DOS was not mixed, that is, Example 2 was a urethane composition consisting of only a prepolymer. <Test Evaluation Method> The urethane composition according to each of the above examples was used for 60
C. and 80.degree. C., and the viscosity of the urethane composition at each temperature was measured with a BL viscometer. <Test Evaluation Results> The test results are shown in Table 1.

[0039]

[Table 1]

According to the table, it is possible to reduce the viscosity of the urethane composition by mixing a plasticizer, but the effect is larger when mixing DOS than when mixing DOP. Can be confirmed. The reason for this is not clear, but it is thought that DOS is more compatible with the urethane prepolymer than DOS. Therefore, by using DOS as the plasticizer, the workability of the casting process becomes better than before. (Physical Properties of Polyurethane Composition) <Test Evaluation Samples> Test evaluation samples according to the following examples were prepared. The composition is also shown in Table 2. Example 2 A prepolymer having an isocyanate concentration of 5.6% synthesized from PTMG having a molecular weight of 1000 and TDI was placed in a heat-resistant container, and degassed under reduced pressure while controlling the temperature at 80 ° C. Next, with respect to 100 parts by weight of the prepolymer, 17 parts by weight of M
OCA, 0.4 parts by weight of oleic acid, and 20 parts by weight of DOS were put in another heat-resistant container, and stirred at a temperature of 100 ° C. to form a uniform solution. Then, a mixture such as MOCA was added to the prepolymer, followed by stirring and mixing. This was poured into a mold previously placed in an oven controlled at 100 ° C., and the mold was held in the oven for 60 minutes to cause a curing reaction of the urethane composition. The sheet-like polyurethane composition having a thickness of 2 mm thus obtained was prepared in Example 2.
And Comparative Example 3 The same polyurethane composition as in Example 2 was used as Comparative Example 3 except that DOP was used as a plasticizer. That is, it is a polyurethane composition according to a conventional example. Comparative Example 4 Comparative Example 4 was the same polyurethane composition as in Example 2 except that di- (2-ethylhexyl) azelate (DOZ) was used as a plasticizer. Comparative Example 5 The same polyurethane composition as in Example 2 was used as Comparative Example 5 except that a trimellitic acid mixed ester plasticizer (Adekaizer C79 manufactured by Asahi Denka Kogyo KK) was used as the plasticizer.

[0041]

[Table 2]

<Test Evaluation Method> -Tensile Properties- A dumbbell-shaped test piece was cut out from the polyurethane composition sheet according to each of the above examples, and this was cut into JIS K6301.
A tensile test was performed in accordance with the above, and data on the breaking strength and the breaking elongation were collected. -Tear property- A test piece for a tear test in the shape of a "<" is cut out from the polyurethane composition sheet according to each of the above examples, and this is subjected to JI.
A tear test was performed according to SK6301, and data on tear strength was collected. -Friction characteristics-The friction coefficient of the polyurethane composition according to each example was measured using a friction coefficient measurement tester shown in Fig. 2.

A square sample of 5 mm square was cut out from the polyurethane composition sheet according to each of the above examples. Next, as shown in FIG. 2, the sample 16 was attached to the sample fixture 11. At this time, the distance from the fixture support shaft 12 to the sample 16 was set to 50 mm, and the distance from the sample 16 to the load cell 15 was set to 50 mm (the distance from the fixture support shaft 12 to the load cell 15 was set to the fixture support shaft 12). From sample 1
6 times the distance between 6). Then, the sample was pressed against the friction disc 13 so that a load (W) of 10 N was applied to the sample. In this state, the friction disk 13 was rotated at 50 rpm, and the force (F) acting on the load cell 15 was detected. Here, the distance from the fixture support shaft 12 to the load cell 15 is two times the distance between the fixture support shaft 12 and the sample 16.
Since it is doubled, the frictional force acting on the sample is twice the force detected by the load cell. Therefore, load cell 1
5 times the load (W) of 10N
That is, the friction coefficient of each example was obtained by the calculation of the equation “friction coefficient μ = 2F / W”. <Test Evaluation Results> The test results are shown in Table 3.

[0044]

[Table 3]

According to the table, comparing Example 2 in which DOS was mixed as a plasticizer with Comparative Example 3 in which DOP was mixed, it can be confirmed that the tensile properties and the tear properties were at the same level. The reason for this is not clear, but D
It is considered that both OP and DOS have the same degree of interaction with the polyurethane molecular skeleton, so that there is no difference in their influence on the physical properties of the polyurethane composition. Further, it is considered that the reason why the friction coefficient of Example 2 is smaller than that of Comparative Example 3 is that DOS has a property of bleeding more easily than DOS. Therefore, in the case of a toothed belt, the noise during belt running can be reduced as compared with the conventional case by using DOS as the plasticizer.

Next, when comparing Example 2 with Comparative Examples 4 and 5 in which other plasticizers are mixed, it can be confirmed that Comparative Examples 4 and 5 have inferior tensile and tear properties as compared with Example 2. . The reason for this is not clear, but the di-
The (2-ethylhexyl) azelate and the trimellitic acid mixed ester plasticizer of Comparative Example 5 have poorer compatibility with the polyurethane skeleton than DOS or DOP. For this reason, it is considered that the dispersion in the polyurethane matrix is poor, and the polyurethane composition is easily cracked, resulting in a decrease in fracture characteristics such as breaking strength and tear strength.
The reason why the coefficient of friction of Example 2 is smaller than those of the other comparative examples is considered to be due to the difference in the bleeding property and the difference in the dispersion state of the plasticizer in the urethane matrix.

[Brief description of the drawings]

FIG. 1 is a side view of a toothed belt B according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a friction coefficient measurement tester.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Belt main body 2 Belt tooth 3 Core wire 4 Reinforcement cloth 11 Sample fixture 12 Fixture support shaft 13 Friction disc 14 Friction disc rotation axis 15 Load cell 16 Sample B Toothed belt

Claims (6)

[Claims] 1. A urethane composition for forming a belt, which is used for producing a urethane belt by injecting into a mold for forming a belt and performing a curing reaction, and produced by synthesizing a polyol and a polyisocyanate. Di- (2-ethylhexyl) to urethane prepolymer
A urethane composition for forming a belt, comprising a mixture of sebacate. 2. The urethane for forming a belt according to claim 1, wherein the mixing amount of the di- (2-ethylhexyl) sebacate is 3 to 40 parts by weight based on 100 parts by weight of the prepolymer. Composition. 3. The urethane composition for forming a belt according to claim 1, wherein the polyol is a polyether glycol. 4. The belt molding according to claim 1, wherein an amine compound is mixed as a curing agent so that a polyurethane urea composition is formed by a curing reaction. Urethane composition. 5. A power transmission belt comprising a belt main body formed of the urethane composition for forming a belt according to any one of claims 1 to 4. 6. The transmission belt according to claim 5, wherein the belt main body is a toothed belt main body.