JPH0149741B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a sheet made of polyester elastomer, particularly a sheet suitable for use in belts. So-called thermoplastic polyester elastomers synthesized from aromatic dicarboxylic acids, aliphatic glycols, and α,ω-dihydroxy aliphatic polyethers generally have a high melting point, excellent chemical resistance and flex fatigue resistance, and are crystalline resins. For this reason, it has characteristics such as superior cleaving resistance compared to other thermoplastic elastomers with low crystallinity such as polyurethane. These characteristics are suitable for belts, and there have been attempts to use molded polyester elastomer sheets alone as conveyor belts for light loads. However, the above-mentioned single-sheet belt has the drawback that a creep phenomenon occurs and the belt stretches when the tensile load is large or the ambient temperature is high. In order to prevent the creep phenomenon, it is sufficient to bond canvas or the like together, but in such a case, the adhesive used for bonding and the material of the canvas will have a considerable effect. For example, polyester elastomer itself has excellent heat aging resistance, but the adhesive performance, heat aging resistance, flexibility, etc., is lower than that, and it also has the disadvantage of causing delamination during use, so it is difficult to use composite belts. Not only is the range of use extremely limited, but it also has drawbacks such as poor durability. If the creep resistance of a single sheet can be dramatically improved, it will become the ideal belt that is the simplest, lightest, has no problems with fraying of the canvas or delamination between the sheet and the canvas, and is also highly hygienic. . If a single sheet is stretched uniaxially or biaxially, the sheet will be strong and have excellent creep resistance. However, when performing so-called tensile stretching, the entire sheet is initially stretched almost uniformly, but the tension of the material Because the so-called netting phenomenon occurs where the material begins to stretch with local constrictions beyond the yield point, a stretching ratio of approximately 5 to 8 times is usually required to uniformly stretch the entire material. Therefore, for example, in order to obtain a final sheet with a thickness of 1 mm, a raw sheet with a thickness of at least about 5 mm is required in the case of uniaxial stretching, and an even thicker raw sheet is required in the case of biaxial stretching. . In order to make such a thick and wide sheet and stretch it, great force and equipment are required, which not only poses many practical difficulties, but is also completely disadvantageous economically. Furthermore, when preheating the raw sheet before stretching, if the thickness is large, there are operational disadvantages such as difficulty in uniformly heating the sheet in a short time. Another major drawback is that uniaxially stretched sheets are extremely susceptible to tearing in the warp direction. As a result of intensive research into a method for producing a sheet that achieves a stretching effect without causing the netting phenomenon, the inventors of the present invention discovered that, completely unexpectedly, the polyester elastomer was stretched to some extent in the width direction on a roll while at the same time in the length direction. By further stretching, that is, rolling, we succeeded in obtaining a stretching effect without the phenomenon of netting, and arrived at the method of the present invention. That is, the present invention is characterized by melt-forming a crystalline polyester elastomer having a melting point of 140° C. or higher into a sheet or plate, and then rolling it in the width direction while simultaneously rolling it in the length direction and heat-treating it. According to the present invention, there is no netting phenomenon and 2~
Even at a rolling ratio of about 3 times, the entire sheet can be sufficiently and uniformly stretched, and the strength can be increased to a level comparable to that of a tensile stretched sheet of about 5 to 8 times, and the uniaxially stretched sheet is less likely to tear in the longitudinal direction. It is possible to obtain a sheet with excellent tear strength. Such a stretching effect by rolling is only obtained when the high melting point and crystalline polyester elastomer of the present invention is rolled, and even when thermoplastic polyurethane elastomer is rolled, almost no improvement effect is seen in terms of creep resistance. do not have. Further, among polyester elastomers, polymers with low crystallinity and a melting point of 140° C. or less cannot be rolled to obtain the expected improvement effect. The reason why the polyester elastomer of the present invention exhibits excellent effects is thought to be because it has a high melting point, high crystallinity, and a clear tensile yield point. The polyester elastomer used in the present invention includes polyethylene terephthalate,
Aromatic polyesters such as polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene terephthalate/isophthalate, polyethylene terephthalate/butylene terephthalate are used as hard segments, and polyethylene ether glycol, polybutylene ether glycol, polyethylene ether glycol/polybutylene ether glycol A polyester polyether block copolymer having α,ω-dihydroxy aliphatic polyether as a soft segment, such as polyester polyether block copolymer having the aromatic polyester as a hard segment, polyethylene adipate, polyethylene sebacate, polybutylene adipate, polyethylene adipate/butylene adipate. , α, ω like polycabrolactone
- Polyester polyester block copolymer with dihydroxy aliphatic polyester as a soft segment, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid and adipic acid, sebacic acid,
Examples include random copolymers with aliphatic carboxylic acids such as azelaic acid, dimer acid, and ω-caprolactone and diols such as ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexanedimethanol. The above α,ω-dihydroxy aliphatic polyether and α,ω-dihydroxy aliphatic polyester usually have an average molecular weight of 400 to 6,000, preferably 800 to 3,000. Of course, the above-mentioned polyester elastomer may be a blend of two or more types, or may be a polyester elastomer that is a combination of two or more different types of soft segments, such as polyether and polyester. A particularly preferred polyester elastomer is one in which a small amount of a branched component such as trimellitic acid or glycerin is copolymerized, or an elastomer in which the terminal carboxyl group of the elastomer is blocked with an epoxy compound or the like to stabilize it. Aromatic dicarbons, aliphatic glycols and α,ω-dihydroxy aliphatic polyethers with an average molecular weight of 400 to 6000,
It is a polyester elastomer obtained from at least one compound selected from α,ω-dihydroxy aliphatic polyesters having 400 to 6000 carbon atoms and aliphatic dicarboxylic acids having 10 or more carbon atoms. The polyester elastomer must be a crystalline polyester elastomer having a melting point of 140°C or higher, and particularly preferably a melting point of 160°C or higher. The proportion of the soft segment in the polyester elastomer is preferably about 10 to 80% by weight, although it varies somewhat depending on the composition. Depending on the application, additives such as organic or inorganic fillers, nucleating agents, stabilizers, conductive agents, flame retardants,
Although coloring agents, lubricants, etc. can be added, it is of course preferable that no additives or a minimum amount be added in applications that directly contact foods, such as food conveyance belts. A polyester elastomer is usually formed into a sheet or plate by melt extrusion, and then the sheet or plate is rolled using rolling rolls at a rolling ratio of 2 to 7 times in the machine direction and 1 to 2 times in the width direction (width direction). It is rolled about twice as much. When the rolling ratio in the longitudinal direction is 7 times or more, a disadvantage arises in that the splitting property (vertical tearing property) becomes noticeable. In addition, from the viewpoint of rolling properties, the temperature of the sheet or plate during rolling is usually within the range of at least the glass transition point of the polyester elastomer and at least 30°C lower than the melting point, preferably from room temperature to at least 50°C lower than the melting point. It is preferable that Note that the thickness of the sheet or plate-shaped body before rolling is preferably formed to a thickness that gives a sheet having a thickness of about 0.1 to 10 mm after rolling. It is important to heat-treat the rolled sheet so that the sheet does not change in size or deteriorate in performance when used in a high-temperature atmosphere. The heat treatment is preferably carried out at a temperature higher than the use temperature in consideration of the use environment of the sheet, but since heat treatment at a temperature too close to the melting point will reduce the rolling effect, the heat treatment should be carried out at a temperature at least 10°C lower, preferably at least 10°C. Keep the temperature at least 20℃ lower. In addition, although heat treatment is generally carried out at a fixed length, it is also possible to heat set while causing some shrinkage, and by doing so, the final sheet
Md (modulus of elasticity) can be changed. The present invention will be explained below with reference to Examples. Example Polyester polyether elastomer synthesized from terephthalic acid, 1,4-butanediol and polytetramethylene ether glycol with an average molecular weight of 1000 [melting point 200°C, polytetramethylene ether glycol content 40%, intrinsic viscosity (phenol/tetra Chloroethane = 3/2 weight ratio
(measured at 30℃) 0.9] sheet (thickness 3mm, width 500mm)
mm) was molded by extrusion molding using a conventional method. The extrusion molding temperature was 220°C, and the chill roll temperature was 50°C. The sheet was rolled under the following conditions and then heat treated. The sheet was heated through a preheating chamber set at 80°C, and then rolled between rolling rolls heated to 100°C to 1.2 times the width in the width direction and 2.5 times the length in the machine direction. Note that the magnification in the longitudinal direction was adjusted by the ratio of the circumferential speed of the rolling roll and the take-up roll, and the magnification in the width direction was adjusted by the press pressure of the rolling roll. The rolled sheet is continuously heated to 160℃ on the take-up roll.
The material was heat-set by passing it through a heating chamber at a fixed length. The feeding speed at this time was 15 m/min, and the heat setting time was 2 minutes. The physical properties of the obtained rolled and heat treated sheet were evaluated and the results are shown in Table 1. For comparison, the physical properties of an extruded unstretched sheet that was uniaxially stretched 5 times at 100°C and heat-set at 160°C are also shown.

[Table] The superiority of the rolling method of the present invention in terms of longitudinal tear resistance is clearly recognized.
In addition, the stress-elongation curve (SS curve) of the rolled and heat-treated sheet is shown in Figure 1, the temperature dependence of the SS curve is shown in Figure 2, and the creep resistance (100℃
Fig. 3 shows the tensile creep in Fig. 3. It can be seen that the strength is increased by rolling and heat treatment, the change in Md with respect to temperature is greatly improved, and the creep resistance is greatly improved, resulting in a sheet with excellent physical properties. The sheet was used as a belt with good results.

[Brief explanation of drawings]

Fig. 1 is a drawing showing an example of the S-S curve of an unrolled sheet and a rolled sheet, and Fig. 2 is a drawing showing an example of the S-S curve of an unrolled sheet and a rolled sheet.
Figure 3 shows the temperature dependence of the curve and the creep resistance (tensile creep at 100°C).

Claims (1)

[Claims] 1. A crystalline polyester elastomer having a melting point of 140°C or more is melt-molded into a sheet or plate, and then rolled in the width direction and simultaneously rolled in the length direction and heat treated. A method for producing a polyester elastomer sheet. 2 The polyester elastomer contains aromatic dicarboxylic acid, aliphatic glycol and an average molecular weight of 400.
At least one compound selected from α, ω-dihydroxy aliphatic polyethers having an average molecular weight of 400 to 6,000, α, ω-dihydroxy aliphatic polyesters having an average molecular weight of 400 to 6,000, and aliphatic dicarboxylic acids having 10 or more carbon atoms. The method for producing a polyester elastomer sheet according to claim 1, which is the obtained polyester elastomer. 3. The polyester elastomer sheet according to claim 1, wherein the rolling conditions are within a temperature range of at least the glass transition point of the polyester elastomer and at least 30°C lower than the melting point, and at a rolling ratio of 7 times or less in the longitudinal direction. manufacturing method. 4. The method for producing a polyester elastomer sheet according to claim 1, wherein the heat treatment temperature is at least 20°C lower than the melting point of the polyester elastomer.