JPS645820B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to elastic molded bodies, specifically, ducts, hoses, tubes, etc. used in transportation machines such as automobiles and motorcycles, construction machines such as bulldozers, industrial machines such as robots, and machine tools and hydraulic and pneumatic machines. This invention relates to hollow-molded elastic molded bodies such as seal members and cover members. In various industrial fields, from the standpoint of resource and energy conservation, elastic molded bodies such as ducts, which were traditionally manufactured mainly from rubber, are being replaced with soft polyvinyl chloride (hereinafter abbreviated as PVC), which does not require a vulcanization process.
Construction using thermoplastic elastomers such as Generally, elastic molded bodies made of PVC are flexible,
It also has relatively excellent characteristics in terms of elasticity and moldability. However, on the other hand, it is inferior to conventional vulcanized rubber in mechanical strength such as tensile strength and tear resistance, and is also inferior in oil resistance to grease, gasoline, etc., and cannot be used in applications that require these properties. There were flaws. The present invention was developed in consideration of the above, and as a result of intensive research and experiments in order to solve the above problems, the present inventors have developed an elastic molded body formed by blow molding that meets ASTM D-638.
It must be composed of at least two layers: a layer made of PVC with a tensile modulus of 2000 Kg/cm ² or less, and a layer made of a thermoplastic polyamide elastomer (hereinafter abbreviated as TPA) with a tensile modulus higher than the PVC layer. As a result, it was possible to obtain an elastic molded article that has excellent mechanical strength such as tensile strength and tear resistance and oil resistance that cannot be obtained with an elastic molded article made of a single PVC layer, and also has an excellent impact modulus. 2000Kg/used for the elastic molded body according to the present invention
Flexible polyvinyl chloride (PVC) with a tensile modulus below cm ² has an average degree of polymerization () of 800 to
12,000, preferably 1,300 to 10,000, and 30 to 220 parts of a plasticizer per 100 parts of the polyvinyl chloride, and other fillers, stabilizers, stabilizing aids, pigments, etc. They can also be blended as appropriate. As the plasticizer, phthalate-based, epoxy-based, phosphoric ester-based, fatty acid ester-based, linear dibasic ester-based, or polyester-based plasticizers can be used, but in the present invention, the type of plasticizer is not particularly important. It is not limited. If the average degree of polymerization of the polyvinyl chloride is less than 800, the tensile strength will decrease, and if it exceeds 12,000, the appearance of the surface of the parison during molding will be poor and the moldability will be extremely poor.
Furthermore, if the plasticizer is less than 30 parts, it becomes inelastic, and if it exceeds 220 parts, the tensile strength is significantly reduced. A polyamide elastomer is a multi-block copolymer having a soft segment composed mostly of aliphatic polyether, aliphatic polyester, or aliphatic polyether, and a hard segment composed of polyamide or the like. In principle, various types of polyamide elastomers can be obtained by changing the types and proportions of dibasic acids, diamines, glycols, and polyamides, polyethers, and polyesters. For example, polyamides include polycabramide, polyhexamethylene adipamide, polyhexamethylene sebacamide, polyundecaneamide,
Examples of the aliphatic polyether include polytetramethylene oxide, polypropylene oxide, polyethylene oxide, etc., and examples of the aliphatic polyester include polyethylene adipate, polycaprolactone, polyethylene sebacate, etc. The elastic molded article according to the present invention is composed of at least two layers, a PVC layer and a TPA layer, and in order to obtain an elastic molded article that is flexible and has excellent elasticity, the PVC constituting the elastic molded article has a tensile modulus. of
By setting the tensile modulus to 2000Kg/cm ² or less and setting the tensile modulus of TPA higher than that of PVC when laminating PVC and TPA, we were able to obtain a superior rebound modulus compared to simply laminating. . On the other hand, as described above, the elastic molded body of the present invention is suitable for use in ducts used in transportation machines such as automobiles and motorcycles, construction machines such as bulldozers, industrial machines such as robots, machine tools, hydraulic and pneumatic machines, etc. , hoses, tubes, other sealing members, cover members, etc.
It has elasticity and is a hollow molded body. For example, when the elastic molded article according to the present invention is used as a shock absorber boot, a steering boot, or a constant velocity joint boot of an automobile,
In addition to being able to demonstrate its characteristics well,
This is preferable because the boot does not crack due to flying pebbles, or the end connection location does not come off due to loss of elasticity. In addition, the above-mentioned elastic molded body is formed by blow molding, which involves coextruding a plasticized thermoplastic elastomer into a multilayer tubular parison or multilayer sheet, and then shaping it into a three-dimensional shape using positive or negative pressure. It is molded into As mentioned above, the lamination at this time is ASTM
D-638, it is composed of at least two layers: a layer made of PVC with a tensile modulus of 2000 Kg/cm ² or less, and a layer made of TPA, which has a higher tensile modulus than the PVC layer. It may be constructed in three layers, with the layer being TPA and the middle layer being PVC. Further, thermoplastic plastics or elastomers thereof may be further laminated within a range that does not significantly impair the effects of the present invention. In addition, within the PVC layer no more than 50%
Polymers with good compatibility with PVC, such as TPA, can be mixed. As a means for further laminating, a multilayer blow molding method using coextrusion is used, but in particular, the overall thickness composition ratio of the TPA layer and PVC layer is 90:10 to 0.5:
99.5, preferably 50:50 to 0.5:99.5, there is no drawdown of the parison and the parison itself can be molded into the mold cavity shape in good condition, so the wall thickness of the elastic molded body is uniform and good. High elasticity can be expected. Furthermore, the interlayer adhesion strength of the elastic molded articles according to the present invention was all very high, and molded articles that could not be peeled off were obtained. [Example 1] PVC-(1) and TPA-(1) shown in Table 1 were each made with a screw diameter of 50 mm and a screw length (L/D) of 2.
Melt and knead in the extruder No. 2, and join the outer layer with TPA and the inner layer with PVC in an extrusion die to form an outer diameter of 40 mm.
mm, co-extruded as a cylindrical two-layer parison with an average wall thickness of 2 mm (thickness composition ratio of outer layer and inner layer 20:80), and the extruded parison is closed in a split mold and compressed. By blowing air and performing hollow molding, a molded article A having a bellows portion 1 and connecting portions 2, 2 at both ends as shown in FIG. 1 was obtained. The molded product A has a length of 200 mm, a bellows portion diameter of 60 mm,
The valley diameter is 45mm, the average wall thickness is 0.7mm, and the thickness is 11.5mm.
As shown in FIG. 2, it is composed of two layers: an inner layer 3 made of PVC and an outer layer 4 made of TPA. [Example 2] PVC-(2) and TPA-(2) shown in Table 1 were extruded using an extruder to make the middle layer PVC and the inner and outer layers.
Molded product B as shown in Figure 3 was obtained by bonding as TPA, coextruding it as a three-layer parison with the wall thickness composition ratio of outer layer, middle layer, and inner layer set at 10:80:10, and blow molding. Ta. The shape of the molded product B is approximately the same as the molded product A according to Example 1,
It is composed of three layers: an inner layer 5 and an outer layer 6 made of TPA, and an intermediate layer 7 made of PVC. Note that the specifications of the extruder, the dimensions of the parison, and the shape of the molded product are the same as in [Example 1]. [Example 3] PVC-(1) shown in Table 1 mixed with 30% TPA-(2) was used as the intermediate layer, TPA-(2) was used as the inner layer and outer layer, and the wall thickness composition ratio was 15: With the same specifications and means as [Example 2] except that the ratio is 70:15, the first
A molded article C having the same shape as shown in the figure was obtained. [Comparative Example 1] Using PVC-(2) shown in Table 1, the first
A molded article D having the same shape as shown in the figure was obtained. Note that the specifications of the extruder and the dimensions of the parison are the same as in [Example 1]. [Comparative Example 2] Molded product E was obtained using the same specifications and methods as [Example 1] except that PVC-(3) and TPA-(1) shown in Table 1 were used. [Comparative Example 3] A molded product F was obtained using the same specifications and methods as [Example 2] except that PVC-(3) and TPA-(2) were used. Table 2 shows the results of testing the characteristics of the molded products A to D obtained in Examples 1 to 3 and Comparative Example 1. In addition, each [Examples 1 to 3] and each [Comparative Examples 1 to 3]
Table 3 shows the results of testing the impact resilience modulus of each of the molded products A to F obtained in [3].

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【table】

【table】

[Piercing strength]

A part of the wall of the molded product obtained in Examples and Comparative Examples was cut out to use as a sample, and the periphery of the sample was fixed with a fixing frame having an opening of 10 mm in diameter. A needle formed into a round shape with a radius of curvature of 0.5 mm was heated at 20℃ and 65%RH for 50 minutes.
Pierce at a speed of ±5 mm/min., measure the maximum load until the needle penetrates, and divide the value by the wall thickness of the sample. This test method is practical as an evaluation method for molded products from which samples are collected under harsh conditions, for example, when the molded products are subjected to collisions with sharp pebbles or the like. [Heat resistance] Fix the upper end of the molded product, suspend a weight with a constant load from the lower end, set it in a high temperature atmosphere for a certain period of time, and measure the change in length of the molded product. η (%) = l - l ₀ / l ₀ × 100 η... Rate of change of molded product l ₀ ... A 100 g weight is suspended at 20°C and 65% RH.
Length of the molded product after 1 hour l...Hang a 100g weight at 120℃, length after 1 hour [Rebound modulus] Check one end of the molded product under the conditions of 20℃ and 65% RH. 200 and place the other end on the load cell.
Compress at a speed of mm/min. to completely form a bellows.
After the valley is completely in contact, it will restore itself at the same speed,
The load at that time was measured, and the relationship between the load and the amount of change was recorded as a hysteresis curve as shown in FIG. (%) = A ₁ / A ₀ × 100 ...Repulsion elasticity modulus of the molded product A _{0 ...Area surrounded by l 1 ,} a, and the X-axis A ₁ ......L ₂ , a, and the X-axis The area enclosed by a perfectly elastic body approaches 100. Also,
As a molded product that can be used in a wide range of applications, excellent impact resilience is an important property and is a practical method for evaluating molded products. As a result of comparing the characteristics of each molded article of the above example and comparative example, as shown in Table 2, the molded article according to the example of the present invention is different from the conventional molded article shown in [comparative example 1].
It can be seen that it has excellent mechanical strength such as tensile strength, tear strength, and puncture strength, which cannot be obtained with an elastic molded body made of PVC alone, and excellent oil resistance against grease, gasoline, etc. In addition, the tensile modulus is 2000Kg/ ^cm2 or more.
PVC and TPA with lower tensile modulus than PVC
As shown in Table 3, the molded bodies shown in Comparative Examples 2 and 3 cannot have an excellent impact modulus, which is one of the important performances of the present invention. Incidentally, the desirable impact resilience modulus of the elastic molded article in the present invention is 40% or more, particularly preferably 70% or more. Further, the desirable tensile modulus of the molded product shown in the above examples is 30 to 1200 kg/cm ² (ASTM D-
638), and the desirable tensile modulus of the PVC constituting this molded product is 25 to 1100 Kg/cm ² ,
TPA is 150-5000Kg/ ^cm2 . The hardness of the elastic molded article according to the present invention can be appropriately set depending on the intended use without changing the gist of the present invention. For example, when used in automobile ducts such as shock absorber boots, steering boots, and constant velocity joint boots,
Increase the tensile modulus of TPA to 200Kg/cm2 ^or more,
The tensile modulus of PVC is set to 500Kg/ ^cm2 or less, and the overall thickness composition ratio of the TPA layer and PVC layer is
If the ratio is 50:50 to 0.5:99.5, it has excellent mechanical strength and rebound modulus, and is suitable as an automobile duct. In addition, in the above [Example 1], the outer layer is
An example of a two-layer structure with TPA and PVC as the inner layer is shown, but depending on the usage conditions of the molded product, the constituent materials of the inner and outer layers may be reversed, with PVC on the outer layer and TPA on the inner layer. . When TPA is placed on the outer layer, due to TPA's puncture strength and oil resistance,
It is resistant to cracks caused by flying pebbles from the outside, prevents deterioration due to gasoline adhesion, and if TPA is placed on the inner layer, oil resistance can be imparted to the inner layer for the same reason. Furthermore, although virgin material is preferable for the PVC used in the above examples, scrap generated in manufacturing the molded product according to the present invention, i.e.
PVC containing a small amount of TPA may be mixed to the extent that the effects of the present invention are not impaired.

[Brief explanation of drawings]

Fig. 1 is a front view showing an example of an elastic molded article according to the present invention, Fig. 2 is an enlarged sectional view of the main part, Fig. 3 is an enlarged sectional view of the main part of another embodiment, and Fig. 4 is a repulsion FIG. 3 is a diagram showing the relationship between the load and the amount of change when measuring the elastic modulus. 1 is the bellows part, 2 is the connection part, 3 and 5 are the inner layers, 4,
6 is the outer layer and 7 is the middle layer.

Claims (1)

[Claims] 1. An elastic molded body formed by a blow molding method, consisting of a layer made of soft polyvinyl chloride having a tensile modulus of 2000 kg/cm ² or less, and a thermoplastic polyamide elastomer having a tensile modulus higher than that of the soft polyvinyl chloride layer. An elastic molded article comprising at least two layers.