GB2111427A

GB2111427A - Elastic shaped article

Info

Publication number: GB2111427A
Application number: GB08228026A
Authority: GB
Inventors: Takehiko Sumi; Masao Harada; Yoshikazu Iwaya
Original assignee: Kyoraku Co Ltd
Current assignee: Kyoraku Co Ltd
Priority date: 1981-09-30
Filing date: 1982-09-30
Publication date: 1983-07-06
Also published as: DE3236308C2; GB2111427B; FR2513568A1; DE3236308A1; FR2513568B1

Abstract

An elastic, shaped article of a laminated construction of at least two layers, comprising (a) a layer of a soft polyvinyl chloride combining polyvinyl chloride with a plasticizer and (b) a layer of at least one thermoplastic elastomer selected from the group consisting of polyester type elastomers, polyurethane type elastomers, and polyamide type elastomers is useful for production of sleeves, ducts, hoses, tubes, sealing members, covering members, etc for use in various machines. When the plasticizer used has an average molecular weight of at least 700, the elastic, shaped article has improved oil resistance at elevated temperatures.

Description

SPECIFICATION Elastic, shaped article This invention relates to an elastic, shaped article of desirably physical properties formed in part from soft polyvinyl chloride.

Heretofore, such elastic, shaped articles as ducts, hoses, tubes, sealing members and covering members which are used, for example, in transportation machines such as automobiles and motorbicycles, construction machines such as bulldozers, industrial machines such as robots, machine tools, hydraulic machines and pneumatic machines, have usually been manufactured from vulcanized natural or synthetic rubber. However, it has long been desired to find a satisfactory replacement for vulcanized rubber for such uses, for the sake of the preservation of natural resources, and the avoidance of the troublesome and energy-expending vulcanization step.

In various industrial fields, therefore, studies have been made to explore the possibility of using such thermoplastic elastomers as soft polyvinyl chloride, which obviate the necessity of vulcanization, as the raw material for elastic, shaped articles such as automotive sleeves which have heretofore been preponderantly manufactured with vulcanized rubbers.

Generally, elastic, shaped articles made of solft polyvinyl chloride exhibit high flexibility and enjoy relatively satisfactory elasticity and moldability. Unfortunately, they are inferior to the conventional elastic, shaped articles made of vulcanized rubbers in terms of mechanical properties such as tensile strength and tear strength. They also suffer from the disadvantage that their flexibility is gradually impaired as their hardness becomes degraded with time. These materials therefore have failed to find utility in applications which demand these properties. When these elastic, shaped articles are used as sleeves in the steering units of automobiles, for example, they tend to sustain cracks under impact from flying stones and the fitting parts serving to retain the sleeves in position tend to come out as the sleeves are gradually deprived of their flexibility.The known elastic, shaped articles of thermoplastic elastomers are further deficient in thermal resistance and in resistance to oils such as grease, gasoline and lubricants. They have, therefore, suffered from the disadvantage that they are not usable where they are iiable to be heated to elevated temperatures or to be smeared with grease, gasoline and lubricants.

Despite the strong demand for a satisfactory substitute for vulcanized rubbers as the raw material for manufacturing elastic, shaped articles such as sleeves, ducts, hoses, tubes and other members for use in various machines, there has not yet been developed any elastic, shaped article which can meet all the desired requirements as to, for example, flexibility, mechanical strength, thermal resistance and oil resistance, and high moldability.

This invention, therefore, has been directed to the development of a raw material for an elastic, shaped article which can possess satisfactory mechanical strengths such as tensile strength, impact strength and tear strength, thermal and oil resistance and moldability, which retains its hardness on aging, and which has high flexibility.

The present invention provides an elastic, shaped article of a laminated construction of at least two layers, comprising: (a) a layer of soft polyvinyl chloride incorporating 30 to 220 parts by weight of a plasticizer per 100 parts by weight of polyvinyl chloride having an average polymerization degree of 800 to 12,000, and (b) a layer of at least one thermoplastic elastomer selected from the group consisting of polyester type elastomers, polyurethane type elastomers and polyamide type elastomers.

If the elastic, shaped article is required to possess high oil resistance at elevated temperatures, the plasticizer to be incorporated in the soft polyvinyl chloride layer should have an average molecular weight of at least 700.

The present invention also provides a plastics laminate, suitable for forming into an elastic, shaped article, wherein the laminate comprises at least two layers, namely (a) a layer of soft polyvinyl chloride incorporating 30 to 220 parts by weight of a plasticizer per 100 parts by weight of polyvinyl chloride having an average polymerization degree of 800 to 12,000 and (b) a layer of at least one thermoplastic elastomer selected from the group consisting of polyester type elastomers, polyurethane type elastomers and polyamide type elastomers.

The invention will now be described in more detail, making reference to the accompanying drawings, in which: Figure 1 is a partially cutaway front view of a bellows sleeve of a three-layer laminated construction of the present invention; Figure 2 is a diagram illustrating the hysteresis curve used for the measurement of modulus of elastic recovery of the bellows; and Figure 3(A) to (E) are hysteresis curves obtained for the elastic, shaped articles prepared in Examples 7 to 10 and Comparative Experiment 4.

According to the present invention, it has been found that an elastic, shaped article of a laminated construction of at least two layers, comprising a layer of a soft polyvinyl chloride (hereinafter referred to briefly as "soft PVC") and a layer of at least one thermoplastic elastomer (hereinafter referred to briefly as "TE") selected from the group consisting of polyester type elastomers polyurethane type elastomers, and polyamide type elastomers, can be superior to conventional elastic, shaped articles formed solely of soft PVC in terms of oil resistance and thermal resistance, retains better the desirable properties inherent in soft PVC, exhibits improvements in mechanical strengths such as tensile strength, impact strength and tear strength, and retains better its hardness and flexibility on aging.This advantageous combination of properties which, in preferred embodiments at least, is enjoyed by the elastic shaped articles of the present invention is believed to be due to the fact that owing to the oil resistance inherently possessed by the selected TE, the TE layer functions as a barrier membrane between the soft PVC layer and oil, thereby helping to prevent the plasticizer contained in the soft PVC layer from passing into the oil and causing a change in the properties of the soft PVC, and also protecting the soft PVC layer against degradation by the action of the oil. Further, the high mechanical strengths possessed by TE are conferred upon the laminated construction.By the lamination of the soft PVC layer and the TE layer, therefore, there can be obtained an elastic, shaped article which excels in oil resistance as well as in mechanical strengths, thermal resistance, moldability and flexibility.

Although under normal room temperature conditions, an elastic, shaped article comprising a layer of soft PVC and a layer of TE, as described above, can exhibit high resistance to oils with a wide variety of plasticizers for the soft PVC layer, it has been experimentally ascertained that, despite the high oil resistance inherently possessed by the TE layer, the oil resistance of the elastic, shaped article can be degraded under harsh conditions involving an elevated temperature, exceeding 90 C for example, when the plasticizer contained in the soft PVC layer has a low molecular weight.

To be more specific, it has been ascertained that when the elastic, shaped article is placed under such harsh conditions involving an elevated temperature, the oil swells the TE layer, the oil now in the swelled TE layer accelerates separation of the plasticizer of low molecular weight from the soft PVC layer, and the plasticizer in the soft PVC layer passes into the swelled TE layer, with the result that the physical properties inherently possessed by the soft PVC will be degraded and the physical properties inherently possessed by the TE will be impaired. This problem is shown conspicuously particularly when the TE has good compatibility with the soft PVC in the laminated construction.

A diligent study devoted to the elimination of this defect has led to the discovery that when the plasticizer contained in the soft PVC layer has an average molecular weight of at least 700, the passage of the plasticizer from the soft PVC layer to the TE is substantially precluded, so that the oil resistance and other physical properties of the elastic, shaped article are retained intact even when the article is placed under harsh conditions involving an elevated temperature. For the purpose of obtaining an elastic, shaped article which exhibits high oil resistance at an elevated temperature in accordance with this invention, therefore, it is imperative that the plasticizer contained in the soft PVC should possess an average molecular weight of at least 700.

The soft polyvinyl chloride (soft PVC) to be used in the elastic, shaped article of the present invention is obtained by combining 100 parts by weight of polyvinyl chloride having an average polymerization degree (P) of 800 to 12,000, preferably 1,300 to 10,000, with 30 to 220 parts by weight, preferably 40 to 200 parts by weight, of a plasticizer. If the average polymerization degree of the aforementioned polyvinyl chloride is less than 800, the mechanical strengths such as tensile strength are less than are usually desired. If it exceeds 1 2,000, the parison of the laminate during, for example, blow molding has poor surface conditions and the produced article suffers from extremely poor moldability.If the amount of the plasticizer incorporated in the soft PVC is less than 30 parts by weight per 100 parts by weight of polyvinyl chloride, the resulting shaped article fails to acquire the desired flexibility. If it exceeds 220 parts by weight, the shaped article is notably deficient in mechanical strengths such as tensile strength. In order to ensure that the elastic, shaped article of this invention has high flexibility and high elastic recovery, the soft PVC desirably possesses a hardness in the range of 30 to 93 on the Shore A scale. Generally, when the amount of the plasticizer used falls in the range mentioned above, the soft PVC incorporating the plasticizer will have a hardness falling in the range just mentioned, although for a given amount of plasticizer the hardness of the soft PVC is somewhat dependent on the particular plasticizer incorporated.Thus, to ensure that the soft PVC possesses a hardness falling in the aforementioned preferred range, the amount of plasticizer used should be chosen having regard to the particular plasticizer selected. Further, the hardness of the soft PVC is preferably lower than the hardness of TE which forms the or a second layer of the laminated construction of the elastic, shaped article.

Optionally, the soft PVC may suitably incorporate therein various additives such as fillers, stabilizers, stabilizing aids and pigments. Although the soft PVC to be used in this invention is desirably made up of pure materials, flashes or fins occurring during the production of the shaped, article can be tolerated to a limited extent provided that the effect of the present invention is substantially retained intact.

For incorporation into the soft PVC, a wide variety of known plasticizers usable for polyvinyl chloride can be adopted without any particular limitation by kind. Examples of the plasticizer usable for this purpose include, but are not limited to: phthalic esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-n-octyl phthalate, di-n-decyl phthalate, di-n-iauryl phthalate, diisobutyl phthalate, dipentyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, dinonyl phthalate, diisodecyl phthalate, butylbenzyl phthalate, butyloctyl phthalate, methyloleyl phthalate, butyllauryl phthalate, dicyclohexyl phthalafe,-diallyl phthalate, alkyl cyclohexyl phthalate, dimethoxyethyl phthalate and diethoxyethyl phthalate; phosphoric esters such as tributyl phosphate, tributoxyethyl phosphate, tri-2ethylhexyl phosphate, triisodecyl phosphate, triphenyl phosphate, diphenyldecyl phosphate and diallyl phosphate; aliphatic dibasic esters such as di-2-ethylhexyl adipate, diisodecyl adipate, dicapryl adipate, di-n-octyl adipate, di-3,5,5-trimethylhexyl adipate, dimethoxyethyl adipate, dibutoxyethyl adipate, diisobutyl azelate, di-2-ethylhexyl azelate, dicyclohexyl azelate, di-n-hexyl azelate, dibutyl sebacate, di2-ethylhexyl sebacate and diethyl sebacate; alicyclic dibasic esters such as di-2-ethylhexyl tetrahydrophthalate, di-n-octyl tetrahydrophthalate and di-2-ethylhexyl hexahydrophthalate; epoxy plasticizers such as epoxidized soybean oil, epoxidized safflower oil, epoxidized cottonseed oil, allyl epoxystearate, ethyl epoxystearate, glycidyl epoxyoleate, glycidyl epoxystearate and epoxystearyl acrylate; other aliphatic esters such as oleic esters, stearic esters, ricinoleic esters and palmitic esters; aromatic carboxylic esters such as benzoic esters, trimellitic esters, pyromellitic esters and trimesic esters; and polyester type plasticizers obtained by the reaction of dibasic acids with glycols and generally further with chain stoppers.

For the purpose of obtaining an elastic, shaped article which exhibits high resistance to oils under conditions involving an elevated temperature, it is necessary, as already pointed out, to incorporate into the soft PVC a plasticizer having an average molecular weight (M) of at least 700, preferably at least 900. For a plasticizer which satisfies this requirement, the amount of incorporation into the soft PVC is determined as described above. If the average molecular weight of the plasticizer is less than 700, the plasticizer contained in the soft PVC layer is dispersed so much as to pass into the TE layer and even exude out of the laminated construction. For the elastic, shaped article to possess high resistance to oils under conditions involving an elevated temperature, it is imperative that the average molecular weight of the plasticizer should exceed at least 700.

A plasticizer satisfying this requirement can be selected from among polyester type plasticizers and epoxy type plasticizers.

The polyester type plasticizers have structures wherein monobasic acids or monohydric alcohols terminate both ends of chain polyesters as iliustrated by the following formulae: L--GfDD-GfL A-D AGD+nA wherein, L denotes a monobasic acid (such as caproic acid, capric acid, pelargonic acid, lauric acid or oleic acid), A denotes a monohydric alcohol (medium to higher alcohol such as capryl alcohol, lauryl alcohol, oleryl alcohol or stearyl alcohol), G denotes a glycol (such as 1 ,2-propylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, 1 ,3-butanediol, 1 ,4-butane diol, neopentyl glycol or 1,6 hexane diol), and D denotes a dibasic acid (such as sebacic acid, azelaic acid, adipic acid or phthalic acid).

Examples of the epoxy type plasticizer advantageously usable herein include plasticizers obtained by epoxidizing soybean oil, cottonseed oil, sperm oil, etc.

The thermoplastic elastomer (TE) which is used in the elastic, shaped article of the present invention is a high molecular substance which at normal room temperature exhibits elasticity of the kind possessed by vulcanized rubber and which at elevated temperatures is plasticized enough to become moldable. In view of the requirements for adherency to the soft PVC layer, resistance to oils such as grease, gasoline and lubricants, and mechanical strengths such as tensile strength, this thermoplastic elastomer is selected from among polyester type elastomers, polyurethane type elastomers, polyamide type elastomers and combinations of such elastomers.

The polyester type elastomers (hereinafter referred to briefly as "PEE") are multi-block copolymers which have a soft segment preponderantly composed of an aliphatic polyether, an aliphatic polyester, or an aliphatic polyether ester and a hard segment preponderantly composed of a high-melting crystalline aromatic polyester, for example. Theoretically, numerous types of polyester type elastomers may be obtained by varying the kinds and proportions of dibasic acids, glycols, polyesters, and/or polyethers. For example, polytetramethylene terephthalate and polyethylene terephthalate are available as aromatic polyesters and polytetramethylene oxide and polyethylene oxide are available as aliphatic polyethers.

By selecting a polyester type elastomer as TE, there can be obtained an elastic, shaped article which has good oil resistance and elongation and exhibits high adherency to the soft PVC.

The polyurethane type elastomers (hereinafter referred ta briefly as "PUE") are obtained by the polyaddition of polyethers or polyesters and diols with diisocyanate. They embrace those products which additionally use triol, diamine, or triamine in the course of the polyaddition. Diisocyanates include 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and isophorone diisocyanate; glycols include ethylene glycol, 1 ,4-butylene glycol, 1 ,4-hexane diol, bis-hydroxyethyoxy benzene; polyester diols include polyethylene adipate, poly-1 4-butylene adipate, poly-1 6-hexane adipate, polycaprolactone, and polycarbonate; and polyether diols include polyoxytetramethylene glycol.

The polyamide type elastomers (hereinafter referred to briefly as "PAE") are multi-block copolymers which have a soft segment preponderantly composed of an aliphatic polyether, aliphatic polyester, or aliphatic polyether ester and a hard segment preponderantly composed of a polyamide.

Theoretically, various types of polyamide type elastomers can be obtained by varying the kinds and proportions of polyamides, polyethers and polyesters. For example, polyamides include polycapramide, polyhexamethylene adipoamide, polyhexamethylene sebacamide, polyundecanamide and polydodecanamide; aliphatic'polyethers include polytetramethylene oxide and polyethylene oxide; and aliphatic polyesters include polyethylene adipate, polycaprolactone and polyethylene sebacate.

The TE to be used in this invention preferably has a hardness falling in the range of 60 to 99 on the Shore A scale for the purpose of conferring desired mechanical strengths upon the elastic shaped article.

The elastic, shaped article of the present invention can be produced by the blow molding technique. This blow molding preferably comprises co-extruding plasticized soft PVC and TE in the form of a multi-layer parison or multi-layer sheet and thereafter giving the parison or sheet a threedimensional shape by use of positive or negative pressure.

The lamination involved in this case is to give a construction of at least two layers, comprising a layer of soft PVC and a layer of TE. In a specific embodiment, the laminated construction may involve three layers, comprising an inner and an outer layer each of TE and an intermediate layer of soft PVC.

The elastic shaped, article of the present invention preferably has a laminated construction such that the inner layer or outer layer having the possibility of being exposed to contact with a highly permeable oil will be formed of TE. If desired, the laminated construction of the present invention may be superposed by an additional layer of a thermoplastic substance or elastomer insofar as the superposition will not appreciably impair the attainment of the desired properties.

As to the method for effecting lamination, the multi-layer blow molding method by means of coextrusion preferably is used. In this case, the overall wall thickness ratio of the TE layer to the soft PVC layer should desirably fall in the range of 90:10 to 0.5:99.5, preferably 50:50 to 0.5:99.5. When this requirement is fulfilled, the parison is free from the unwanted phenomenon of draw-down and it can be molded advantageously into the shape of the mold cavity. Consequently, the elastic, shaped article produced can be expected to have a uniform wall thickness and exhibit satisfactory elasticity. Moreover, the component layers of the laminate have very high interfacial adhesive strength and, therefore, are substantially inseparable from each other.An elastic, shaped article formed of such a laminated construction preferably possesses a hardness in the range of 60 to 99 on the Shore A scale and elastic recovery by the bellows test described below of at least 40%, preferably at least 70%.

Figure 1 illustrates a bellows sleeve as one typical embodiment of an elastic, shaped article according to the present invention. In the drawing, a bellows sleeve 1 is formed of a three-layer laminated construction, comprising an inner and an outer layer 2,3 each formed of TE and an intermediate layer 4 formed of soft PVC. In the sleeve, "a" denotes the bellows portion and "b" the connecting end portions.

The bellows sleeve described above is obtained by preparing the individual layers each of the material mentioned above, co-extruding the layers to form a multi-layer parison, and blow molding this multi-layer parison.

When an elastic, shaped article of the present invention is molded from a laminated construction of the three layers, TE/soft PVC/TE, it can be readily bent and elongated with relatively small force owing to the high flexibility of the soft PVC. Since the inner and outer layers are both formed of TE, these layers have good impact resistance, oil resistance, weatherability and tensile strength, owing to the fact that these properties are inherent in the selected TE. Thus, the elastic, shaped article is resistant to fractures due to impact from flying stones and is not substantially degraded by grease and other oils and fats, ozone, water, hot water and detergents such as are used for washing cars. Further, an elastic, shaped article of this three-layer laminated construction enjoys a higher tensile strength than an elastic, shaped article formed solely of soft PVC.Further, because the soft PVC is protected by the opposed coats (layers) of TE, the elastic, shaped article experiences little change of hardness at low temperature and retains its flexibility at low temperatures, whilst even at elevated temperatures, it is not substantially deformed.

When the elastic, shaped article is produced from a three-layer laminated construction comprising an intermediate layer of soft PVC and an inner and an outer layer each of TE, with the proportion of the wall thickness of the soft PVC layer to the total wall thickness of the laminate chosen to exceed 10% but not to exceed 99.5%, the shaped article has good flexibility and uniformity of wall thickness. If, however, the wall thickness ratio of the soft PVC layer is less than 10%, the extruded parison may suffer from heavy draw-down and the production of the shaped article entails high defective molding ratio, making it no ionger possible to produce elastic, shaped articles of uniform wall thickness consistently. Further, the elastic, shaped article may have its flexibility impaired, so that, for example, an end portion cannot be connected to another fitting member with adequate sealability. If, on the other hand, the wall thickness ratio of the soft PVC layer exceeds 99.5%, the TE layer may fail to form a complete layer where the blow ratio of the shaped article is higher. Consequently, the elastic, shaped article produced is deprived of the properties of TE layer and is liable to sustain pinholes in the course of molding. Thus, the production of the shaped article can suffer from a high defective molding ratio.

When the elastic, shaped article is obtained by the blow molding method from a laminated construction of the two layers, soft PVC/TE, the to layer side of the article helps to maintain impact resistance, oil resistance, and tensile strength at high levels, whilst the PVC layer side helps maintain flexibility and moldability. Thus, the operation and effect of such elastic, shaped articles are substantially the same as for the three-layer laminated construction described above.

The elastic, shaped article according to the present invention is useful for the production of sleeves (boots), ducts, hoses, tubes, other sealing members, covering members and so on which are expected to possess elasticity and oil resistance so as to be advantageously used in transportation machines such as automobiles and motor bicycles, construction machines such as bulldozers, industrial machines such as robots, machine tools, hydraulic machines and pneumatic machines. Although the elastic, shaped article of this invention is preferably molded by the blow molding method, it is not necessarily limited to a tubular shape. For example, an elastic, shaped article obtained in a tubuiar shape may then be cut into rings, sheets or small pieces each having the laminated construction comprising a layer of soft PVC and a layer of TE and adapted for various uses.

Depending on the particular use to which the elastic, shaped article according to the present invention is put, the hardness of the article may be suitably selected without departing from the spirit of the invention. When the elastic, shaped article is used in automotive sleeves such as shock absorber sleeves, rack and pinion steering gear sleeves, suspension strut sleeves and constant velocity joint sleeves, suitably high mechanical strengths and high elastic recovery of bellows, can be obtained by selecting the hardness of the TE to be above the level of 60 on the Shore A scale, the hardness of the soft PVC below the level of 87 on the Shore A scale, and the overall wall thickness ratio of the TE layer to the soft PVC layer in the range of 50:50 to 0.5:99.5.Thus, in preferred embodiments, there can be made automotive sleeves which neither sustain cracks under the impact of flying pebbles nor suffer from separation from the parts to which they are joined due to a loss of elasticity.

The present invention is illustrated by the Examples and comparative experiments which follow.

EXAMPLE 1 In an extruder having a screw diameter of 50 mm and a screw ratio of length to the diameter (L/D) of 22, soft PVC-(1 ) and PEE-(1) indicated in Table 1 were melted and kneaded separately. Inside an extrusion die, they were joined as a laminate comprising an outer layer of PEE and an inner layer of soft PVC and coextruded in a cylindrical two-layer parison 40 mm in outside diameter and 2 mm in overall wall thickness (with the wall thickness ratio of the outer layer to the inner layer fixed at 20:80).

The extruded parison was tightly enclosed in a split type mold and then blow molded therein with compressed air. Consequently, there was obtained a shaped article comprising a bellows portion and connecting portions formed at the opposite ends of the bellows portion.

The shaped article had a length of 200 mm, a diameter of 60 mm at the ridge and a diameter of 45 mm at the groove respectively of the bellows portion, a pitch of 1 1.5 mm, and an average wall thickness of 0.7 mm. it has a laminated construction comprising an inner layer of soft PVC and an outer layer of PEE.

EXAMPLE 2 In the same extruder, soft PVC-(2) and PEE-(2) were melted and kneaded separately. Within an extrusion die, they were joined as a laminate comprising an intermediate layer of soft PVC and an inner layer and an outer layer each of PEE and coextruded in a three-layer parison having an outerintermediate-inner wall thickness ratio of 10:80:10. This extruded perison was blow molded to afford a shaped article. The shaped article had a three-layer laminated construction comprising an inner layer and an outer layer each of PEE and an intermediate layer of soft PVC.

The specification of the extruder, the dimensions of the parison, and the shape of the shaped article involved in this example were the same as those of Example 1.

EXAMPLE 3 By following the procedure of Example 2, except that soft PVC-(3) and PEE-(3) were used as the materials and the wall thickness ratio of outer, intermediate, and inner layers was fixed at 1 5:70:1 5, there was obtained a shaped article. In the present example, the specification of the extruder, the dimensions of the parison and the shape of the shaped article were the same as those of Example 1.

COMPARATIVE EXPERIMENT 1 A shaped article was obtained by extruding a parison solely of an polyolefinic elastomer shown in Table 1 and then blow molding the parison. The specification of the extruder, the dimensions of the parison and the shape of the shaped article were the same as those of Example 1.

COMPARATIVE EXPERIMENT2 A shaped article was obtained by extruding a parison solely of soft PVC-(2) and blow molding the parison of soft PVC. The specification of the extruder, the dimensions of the parison and the shape of the shaped article were the same as those of Example 1.

The shaped articles obtained in Examples 1-3 and Comparative Experiments 1-2 as described above were tested for various properties. The results of the test are shown in Table 2.

TABLE 1 Hardness Parts by Kind (Shore A) Composition weight Soft PVC-(1) 70 Polyvinyl chloride (polymerization degree 3000) 100 Polyester type plasticizer (polypropylene adipate, molecular weight 2000) 100 Calcium carbonate 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer} 2 Soft PVC-(2) 78 Polyvinyl chloride (polymerization degree 2500) 100 DOP (di-2-ethylhexyl phthalate) 70 Calcium carbonate 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer) 2 Soft PVC-(3) 79 Polyvinyl chloride (polymerization degree 2500) 100 Rinebole (DL 911 p)(*l) 70 Calcium carbonate 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer) 2 PEE-(1) 96 HYTRELHTG-5612'*2 PEE-(2) 96 PELPRENE P-70B(*3 PEE-(3) 97 HYTREL HTG-4275(* Polyolefinic elastomer 78 TPE 1 800(*4 (*1) Rinebole (DL 911 P): trademark of Shell Chemical Co. for plasticizer, (*2) HYTREL HTG-5612 and -4275: trademarks of DuPont Co. for polyester type elastomers, (*3) PELPRENE P-70B: trademark of Toyobo Co. for polyester type elastomer, (*4) TPE 1800: trademark of Sumitomo Chemical Co. for polyolefinic elastomer.

TABLE 2 Comparative Examples Experiments Properties 1 2 3 1 2 Tensile strength (kg/cm2) 244 268 271 96 1 65 Elongation (%) 377 432 422 320 282 Tear Strength (kg/mm) 94 11 5 117 55 49 Pierce strength (kg/mm) 2.9 3.0 3.0 1.5 1.6 Oil resistance +0 +0 +0 -30 +6 Thermal resistance (%) 7.2 6.2 6.0 26.5 1 5.4 Hardness 83 85 87 91 78 Elastic recovery of bellows (%) 88 88 85 - 69 The data of properties obtained of the shaped articles of the working examples and the comparative experiments shown in Table 2 were determined by the following testing methods.

Tensile strength: JIS K-6301 (kg/cm2) Elongation: JIS K-6301 (%) Tear strength: JIS K-6301,type B (kg/mm) Oil resistance: JIS K-6301 (The sample was left standing in oil, No. 1, at room temperature for 10 days and the change of hardness was measured and the value of change was reported.) Pierce strength: A part of the wall of each of the shaped articles obtained in the working examples and the comparative experiments was cut off and used as a test piece. The test piece was fastened in position with its periphery attached to a stationary frame containing a circular opening 10 mm in diameter.A needle 1 mm in diameter having its tip rounded with a radius of curvature of 0.5 mm was placed on the test piece and lowered down at a speed of 50 + 5 mm/min. under the conditions of 200C and 65% R.H.

The maximum load under which the needle pierced completely through the test piece was measured.

The pierce strength was calculated by dividing the value of the maximum load by the wall thickness of the test piece. This testing method is practical for the evaluation of the shaped article where the shaped article is intended for use under harsh conditions such as involving possible exposure to collision of pebbles with sharp edges.

Thermal resistance: A given shaped article was secured in position by the upper end, with a weight of a fixed load hung down from the lower end thereof. This shaped article was left standing under conditions of an elevated temperature for a stated length of time. The length of the shaped article was measured before and after the standing to find any change in length during the standing as follows:

wherein, : change ratio of shaped article, I,: length of the shaped article after one hour's standing under the load, 1 00 g, of the weight at 200C and 65% R.H.

I,: length of the shaped article after one hour's standing under the load, 1 00 g, of the weight at 1200C.

Hardness: ASTM D-2240 (Shore A) Elastic recovery of bellows: A given shaped article was nipped at one end with a chuck and mounted at the other end on a load cell and was compressed at a rate of 200 mm/min under the conditions of 200C and 65% R.H. until all the ridges and grooves of the bellows portion of the article were brought into tight contact. Then the shaped article was drawn out at the same speed to its original shape. During the return, the load was measured. The magnitude of the load as the function of the amount of change in size was plotted as hysteresis curve.

wherein, (%): elastic recovery of bellows, A,: area enclosed with I,, I, and X axis, and A1: area enclosed with í2, I, and X axis.

The higher the value of 0, the better is the elasticity of the shaped article. For a shaped article to find a wide range of applications, a high value of elastic recovery constitutes an important attribute.

The aforementioned method for testing the elastic recovery of bellows is quite practical for the evaluation of the shaped article.

It is noted from Table 2 which compares the properties of the shaped articles obtained in the working examples with those obtained in the comparative experiments that the shaped articles formed in the working examples of this invention possessed mechanical strengths such as tensile strength, tear strength, pierce strength and elastic recovery of bellows not attained by the conventional elastic shaped articles formed solely of soft PVC in Comparative Experiment 2 and that they possessed excellent thermal resistance and oil resistance not attained by the elastic shaped article formed solely of an ordinary polyolefin type elastomer in Comparative Experiment 1.

EXAMPLE 4 In an extruder having a screw diameter of 50 mm and a screw ratio of length to the diameter (L/D) of 22, soft PVC-(1) and PUE-(1) indicated in Table 3 were melted and kneaded separately. Inside an extrusion die, they were joined as a laminate comprising an outer layer of PUE and an inner layer of soft PVC and coextruded in a cylindrical two-layer parison 40 mm in outside diameter and 2 mm in average wall thickness (with the wall thickness ratio of the outer layer to the inner layer fixed at 20:80). The extruded parison was tightly enclosed in a split type mold and then blow molded therein with compressed air. Consequently, there was obtained a shaped article comprising a bellows portion and connecting portions formed at the opposite ends of the bellows portion.

The shaped article had a length of 200 mm, a diameter of 60 mm at the ridge and a diameter of 40 mm at the groove respectively of the bellows portion, a pitch of 11.5 mm, and an average wall thickness of 0.7 mm. It had a laminated construction comprising an inner layer of soft PVC and an outer layer of PUE.

EXAMPLE 5 In the same extruder, soft PVC-(2) and PUE-(2) were melted and kneaded separately. Within an extrusion die, they were joined as a laminate comprising an intermediate layer of soft PVC and an inner layer and an outer layer each of PUE and co-extruded in a three-layer parison having an outerintermediate-inner wall thickness ratio of 10:80:10. This extruded parison was blow molded to afford a shaped article. This shaped article was substantially identical in shape with the shaped article of Example 4 and had a three-layer laminated construction comprising an inner layer and an outer layer each of PUE and an intermediate layer of soft PVC. The specification of the extruder, the dimensions of the parison, and the shape of the shaped article in this example were the same as those of Example 4.

EXAMPLE 6 By following the procedure of Example 5, except that soft PVC-(3) and PUE-(3) indicated in Table 3 as the materials and the wall thickness ratio of outer, intermediate, and inner layers was fixed at 25:50:25, there was obtained a shaped article. The specification of the extruder, the dimensions of the parison, and the shape of the shaped article in this example were the same as those of Example 5.

COMPARATIVE EXPERIMENT 3 A shaped article was obtained by extruding a parison solely of soft PVC-(2) shown in Table 3 and then blow molding this parison. The specification of the extruder, the dimensions of the parison, and the shape of the shaped article in this example were the same as those of Example 4.

The shaped articles obtained in Examples 4-6 and Comparative Experiment 3 were tested for various properties. The results of the test are shown in Table 4.

TABLE 3 Hardness Parts by Kind (Shore A) Composition weight Soft PVC-(1) 70 Polyvinyl chloride (polymerization degree 3000) 100 Polyester type plasticizer (polypropylene adipate, molecular weight 2000) 100 Calcium carbonate 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer) 2 Soft PVC-(2) 78 Polyvinyl chloride (polymerization degree 2500) 100 DOP (di-2-ethylhexyl phthalate) 70 Calcium carbonate 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer) 2 Soft PVC-(3) 79 Polyvinyl chloride (polymerization degree 2500) 100 Rinebole (DL 911 P) 70 Calcium carbonate 20 Epoxidized Soybean oil 3 Zinc calcium (heat stabilizer) 2 PUE-(1) 90 ELASTOLLAN E-590(* PUE-(2) 85 ELASTOLLAN E-585("2, PUE-(3) 90 ELASTOLLAN E-390*3 (*1) - (*3) ELASTOLLAN E-590, E-585, E-390: trademarks of Japan Elastollan Co. for polyurethane type elastomer.

TABLE 4 Comparative Examples Experiment Properties 4 5 6 3 Tensile strength (kg/cm2) 251 273 295 165 Elongation (%) 395 460 380 282 Tear strength (kg/mm) 107 98 105 49 Pierce strength (kg/mm) 4.7 4.7 5.5 1.6 Oil resistance +0 +1 +1 +6 Thermal resistance (%) 7.4 6.8 6.3 1 5.4 Hardness 85 82 84 78 Elastic recovery of bellows (%) 88 90 87 69 EXAMPLES 7-10 and COMPARATIVE EXPERIMENTS 4 In an extruder having a screw diameter of 50 mm and a screw ratio of length to the diameter (L/D) of 22, the selected thermoplastic elastomer indicated in Table 5 was melted and kneaded.Inside an extrusion die, it was given a layer construction shown in Table 6 (in the case of a multi-layer construction, the individual layers were joined within the extrusion die) and extruded in a cylindrical parison (in the case of a multi-layer construction, coextruded in a cylindrical multi-layer parison) 40 mm in outside diameter and 2 mm in overall wall thickness. This extruded parison was tightly enclosed in a split type metal mold and blow molded therein with compressed air. Consequently, there was obtained a shaped article comprising a bellows portion and connecting portions formed at the opposite ends of the bellows portion.

The shaped article had a length of 200 mm, a diameter of 60 mm at the ridge and a diameter of 45 mm at the groove respectively of the bellows portion, a pitch of 11.5 mm, and an average wal, thickness of 0.7 mm. In Examples 7 and 10, the shaped articles were each in a two-layer construction comprising an inner layer and an outer layer. In Examples 8 and 9, the shaped articles were each in a three-layer construction comprising an inner, an intermediate, and an outer layer. In Comparative Experiment 4, the shaped article were composed solely of soft PVC. The layer constructions of the shaped articles of the working examples of this invention and Comparative Experiment 4 are shown in Table 6.

The data of the physical properties obtained of the shaped articles of the working examples and Comparative Experiment 4 are shown in Table 7 and the hysteresis curves obtained of the shaped articles of Examples 7,8,9 and 10 are indicated in FIGS. 3(A), (B), (C) and (D) respectively and the hysteresis curve obtained of the shaped article of Comparative Experiment 4 is indicated in FIG. 3(E). In the graphs of FIGS. 3, the continuous lines represent the data obtained of the respective shaped articles before their immersion in oil and the dotted lines the data of the same respective shaped articles after their immersion in oil.

TABLE 5 Kind Composition Parts by weight TE-(1) Polyester type elastomer "PELPRENE P-70B" TE-(2) Polyester type elastomer "HYTREL HTG-4275" TE-(3) Polyurethane type elastomer "ELASTOLLAN E-585" TE-(4) Polyamide type elastomer "DIAMIDE PAEI*1 X-3798" TABLE 5 -- Continued Kind Composition Parts by weight Soft PVC-(1) Polyvinyl chloride UP 3,000) 100 Plasticizer (adipic acid-propylene glycol type, M 2,000) 100 Calcium carbonate 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer) 2 Soft PVC-(2) Polyvinyl chloride UP 2500) 100 Plasticizer (adipic acid-propylene glycol type, M 1,000) 70 Talc 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer) 2 Soft PVC-(3) Polyvinyl chloride UP 3,000) 100 Plasticizer (sebacic acid-propylene glycol type, M 2,000) 100 Calcium carbonate 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer) 2 Soft PVC-(4) Polyvinyl chloride UP 2,500) 100 Plasticizer (adipic acid-propylene glycol type, M 1,200) 70 Calcium carbonate 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer) 2 Soft PVC-(5) Polyvinyl chloride UP 2,500) 100 D.O.P. (di-2-ethylhexyl phthalate, M 390) 70 Calcium carbonate 20 Epoxidized soybean oil 3 Zinc calcium (heat stabilizer) 2 (*1) DIAMIDE PAE X-3798: trademark of Daicel Chemical Co. for polyamide type elastomer.

TABLE 6 Comparative Examples Experiment 7 8 9 10 4 Construction Outer layer TE-(1) TE-(2) TE-(3) TE-(4) Intermediate layer - Soft Soft - Soft PVC-(2) PVC-(3) PVC-(5) Inner layer Soft TE-(2) TE-(3) Soft PVC-(1) PVC-(4) Wall thickness ratio outer layer 20 10 15 30 Intermediate layer - 80 70 Inner layer 80 10 15 70 TABLE 7 Comparative Examples Experiment Properties 7 8 9 10 4 Tensile strength (kg/cm2) 244 273 281 178 165 Elongation (%) 375 425 460 340 282 Tear strength (kg/mm) 97 11 9 98 78 43 Pierce strength (kg/mm) 2.6 3.0 5.1 2.4 1.5 Thermal resistance (%) 6.8 5.6 6.9 7.3 17.4 Hardness (before immersion) 87 88 82 83 78 (after immersion) 88 88 84 84 98 Elastic recovery of bellows (before immersion) 85 83 89 82 80 (after immersion) 82 82 83 82 8 The test for hardness and that for elastic recovery of bellows were determined by the following testing methods.

Hardness: (Before immersion) ASTM D-2240 (Shore A) (After immersion) JIS K-6301,with the test piece immersed in oil, No. 3, at 1 200C for 70 hours and tested for hardness after the immersion.

Elastic recovery of bellows: (Before immersion) Same as the testing method described previously.

(After immersion) JIS K-6301, with the test piece immersed in oil, No. 3, at 1 200C for 70 hours and tested for elastic recovery of bellows after the immersion.

It is noted from Table 7 which compares the data of physical properties obtained of the shaped articles of the working examples of this invention with those obtained of the shaped article of Comparative Experiment 4 that the shaped articles formed in the working examples exhibited excellent mechanical strengths such as tensile, tear and pierce strength not attained by the shaped article formed solely of soft PVC in Comparative Experiment 4. Further it is clear from Table 7 and FIGS. 3 that the shaped articles obtained in the working example of this invention showed substantially no change in hardness and elastic recovery of bellows before and after immersion in oil. In contrast, the shaped article obtained in Comparative Experiment 4 showed notable changes in hardness and elastic recovery of bellows before and after immersion in oil. After the immersion in oil, this shaped article showed greatly increased hardness and notably lowered elastic recovery of bellows. These test results indicate that in the shaped articles obtained in accordance with this invention, the plasticizer in the soft PVC layer is prevented from passing into the TE layer and the flexibility and elasticity inherently possessed by soft PVC are retained intact and the oil resistance and mechanical strengths inherent in TE are retained intact even under harsh conditions. Thus, the present invention is capable of producing elastic shaped articles of outstanding properties.

Claims

1. An elastic, shaped article of a laminated construction of at least two layers, comprising (a) a layer of soft polyvinyl chloride incorporating 30 to 220 parts by weight of a plasticizer per 1 00 parts by weight of polyvinyl chloride having an average polymerization degree of 800 to 12,000 and (b) a layer of at least one thermoplastic elastomer selected from the group consisting of polyester type elastomers, polyurethane type elastomers and polyamide type elastomers.

2. An elastic, shaped article according to Claim 1, wherein said soft polyvinyl chloride incorporates 40 to 200 parts by weight of said plasticizer per 100 parts by weight of polyvinyl chloride of an average polymerization degree falling in the range of 1,300 to 10,000.

3. An elastic, shaped article according to Claim 1 or Claim 2, wherein said plasticizer incorporated in said soft polyvinyl chloride is a plasticizer having an average molecular weight of at least 700.

4. An elastic, shaped article according to Claim 3, wherein said plasticizer is a polyester type plasticizer or an epoxy type plasticizer.

5. An elastic, shaped article according to any preceding claim, wherein said soft polyvinyl chloride has lower hardness than said thermoplastic elastomer.

6. An elastic, shaped article according to Claim 5, wherein the hardness of said soft polyvinyl chloride is 30 to 93 and that of said thermoplastic elastomer 60 to 99, both on the Shore A Scale.

7. An elastic, shaped article according to any preceding claim, wherein said elastic, shaped article possesses a hardness of 60 to 99 on the Shore A Scale.

8. An elastic, shaped article according to any preceding claim, wherein the overall wall thickness ratio of the layer of said thermoplastic elastomer to the layer of said soft polyvinyl chloride falls in the range of 90:1 0 to 0.5:99.5.

9. An elastic, shaped article according to Claim 8, wherein the overall wall thickness ratio of the layer of said thermoplastic elastomer to the layer of said soft polyvinyl chloride falls in the range of 50:50 to 0.5:99.5.

10. An elastic, shaped article according to any preceding claim, wherein the layer of said soft polyvinyl chloride and the layer of said thermoplastic elastomer are laminated by co-extrusion.

11. An elastic, shaped article according to any preceding claim, which comprises a three-layer construction having an inner and an outer layer each of thermoplastic elastomer and an intermediate layer of soft polyvinyl chloride.

12. An elastic, shaped article according to Claim 11, which comprises a three-layer construction having an inner and an outer layer each of a polyester type elastomer and an intermediate layer of soft polyvinyl chloride.

1 3. An elastic, shaped article according to Claim 11, which comprises a three-layer construction having an inner and an outer layer each of a polyurethane type elastomer and an intermediate layer of soft- polyvinyl chloride.

14. An elastic, shaped article according to any preceding claim in the form of a hollow tube.

1 5. An elastic, shaped article according to Claim 14, wherein said hollow tube has its opposite ends shaped so as to fit the corresponding ends of members to be joined therewith, and the barrel of said hollow tube between said opposed ends has bellows-structure.

1 6. An elastic, shaped article according to Claim 15, wherein the elastic, shaped article is an automotive sleeve such as a shock absorber sleeve, a rack and pinion steering gear sleeve, a suspension strut sleeve, or a constant velocity joint sleeve.

1 7. A plastics laminate, suitable for forming into an elastic, shaped article, wherein the laminate comprises at least two layers, namely (a) a layer of soft polyvinyl chloride incorporating 30 to 220 parts by weight of a plasticizer per 100 parts by weight of polyvinyl chloride having an average polymerization degree of 800 to 12,000 and (b) a layer of at least one thermoplastic elastomer selected from the group consisting of polyester type elastomers, polyurethane type elastomers and polyamide type elastomers.

1 8. A plastics laminate, or an elastic, shaped article, substantially as described in any one of the Examples herein.