JPH0148143B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an elastic hollow molded body used in ducts of automobiles and the like.

[Conventional technology]

In the automobile field, there is a movement to reduce the weight and cost of automobiles in order to conserve resources and energy, and the use of resin for various parts is being considered.

For ducts, which were conventionally made mainly from rubber, we are considering making them from resin materials.In particular, we are trying to make ducts that will not be destroyed by vibrations when the car is running or that the attached parts will not come off, and that they will not generate noise. In order to prevent this, manufacturing using soft polyvinyl chloride, which has excellent flexibility, is being considered.

[Problems to be Solved by the Invention] However, elastic hollow molded bodies made of soft polyvinyl chloride have a problem in that they are inferior in tensile and impact strength, and their flexibility is impaired due to changes in hardness over time. For example, in the case of a duct covering a constant velocity joint in an automobile, the above-mentioned problems appear as defects such as cracks occurring in the duct due to flying pebbles, and attachment parts coming off due to loss of flexibility.

[Means to solve the problem]

The present invention solves the above problems, and provides an elastic hollow molded article according to the present invention, which is an elastic hollow molded article formed by blow molding, and includes an outer layer made of a thermoplastic elastomer and an intermediate layer made of soft polyvinyl chloride. and an inner layer made of thermoplastic elastomer, with the thickness T ₁ of the outer layer, the thickness T ₂ of the intermediate layer, and the thickness T ₃ of the inner layer being 0.5≦T ₂ / (T ₁ + T ₂ +T ₃ )<0.97.

If the relationship between the wall thicknesses of each of the above values is 0.5>T ₂ / (T ₁ + T ₂ + T ₃ ), the properties of soft polyvinyl chloride, which is superior in flexibility compared to thermoplastic elastomers, can be exhibited. Moreover, when the parison is extruded, the drawdown is severe and the molding defect rate is high, making it impossible to stably obtain an elastic hollow body with a uniform wall thickness, and the flexibility is impaired. For example, there is a drawback that the sealing of the connecting portion between the elastic hollow molded body and other fitting parts is deteriorated. In addition, if T ₂ / (T ₁ + T ₂ + T ₃ ) ≧0.97, the inner and outer layers will not be aligned in the areas where the blow ratio is high during blow molding of the extruded parison, and furthermore, pinholes will occur during molding. This results in a high molding defect rate, and the thermoplastic elastomer cannot exhibit its original properties, which are superior in impact resistance, oil resistance, and tensile strength compared to soft polyvinyl chloride.

Based on the above, the relationship between the thicknesses of each layer was set within the range of 0.5≦T ₂ /(T ₁ +T ₂ +T ₃ )<0.97.

[Effect]

In the present invention, since the outer side of the layer made of soft polyvinyl chloride whose hardness is highly temperature dependent is covered with a thermoplastic elastomer whose hardness is low temperature dependent, the hardness of the soft polyvinyl chloride due to changes in the environmental temperature can be reduced. Changes are suppressed and cracks caused by external stress,
Chemical deterioration is prevented.

In addition, since both the inside and outside of the soft polyvinyl chloride layer are covered with a thermoplastic elastomer layer, the plasticizer added to the polyvinyl chloride will not be leached to the outside, and the hardness will not change over time. most effectively suppressed.

Furthermore, in the present invention, the thickness T ₁ of the outer layer, the thickness T ₂ of the intermediate layer, and the thickness T ₃ of the inner layer are within the range of 0.5≦T ₂ /(T ₁ +T ₂ +T ₃ )<0.97. Because of this, the characteristics of each layer are best exhibited in elastic hollow molded bodies that require flexibility so that they can be easily bent or lengthened with a small force.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a three-layer bellows duct which is an example of an elastic hollow molded body according to the present invention, and the inner and outer layers 2 and 3 of the bellows duct 1 are made of thermoplastic elastomer (hereinafter abbreviated as TPE). , and middle layer 4
is made of soft polyvinyl chloride (hereinafter abbreviated as S.PVC).

The bellows duct 1 is formed by blow-molding a three-layered parison, which is made up of the above-mentioned layers and extruded by co-extrusion. At this time, the thickness T ₁ of the outer layer 3, the thickness T ₂ of the intermediate layer 4, and the thickness T ₃ of the inner layer 2 after molding are within the range of 0.5≦T ₂ / (T ₁ +T ₂ +T ₃ )<0.97. It is composed of.

In the drawings, a is a bellows part, and b, b are connection parts molded on both sides of the bellows part a.

For S.PVC, per 100 parts by weight of polyvinyl chloride.
20~200 plasticizer is blended, and the average degree of polymerization of polyvinyl chloride () is 1300~10000. If the plasticizer is less than 20 parts by weight, it becomes inelastic, and if it exceeds 200 parts by weight, the tensile strength is significantly reduced. In addition, when the average degree of polymerization is less than 1300, the tensile strength decreases,
If it exceeds 10,000, the appearance of the parison surface will be poor and the moldability will be poor.

The above TPE is a polymeric material that exhibits elastic properties like vulcanized rubber at room temperature, but can be plasticized and molded at high temperatures. These include polystyrene, polyolefin, polyurethane, polyamide, polyester, etc., but polyurethane, polyester, and polyamide are preferable.

Polyurethane-based elastomers are obtained by polyaddition of various polyethers or polyester diols and glycols with diisocyanates, and also include those in which triols, diamines, or triamines are used in combination.

Examples of the diisocyanate include 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and isophorone diisocyanate, and examples of the glycol include ethylene glycol, 1,4-butylene glycol,
1,4-hexanediol, bishydroxyethoxybenzene, etc. Polyester diols include polyethylenebate, poly-1,4-butylene adipate, poly-1,6hexane adipate, polycaprolactone, polycarbonate, etc. Examples of the ether diol include polyoxytetramethylene glycol.

Polyester-based elastomers are mostly multi-block copolymers that have a soft segment composed of aliphatic polyether, aliphatic polyester, or aliphatic polyetherester, etc., and a hard segment composed of high-melting point crystalline aromatic polyester, etc. It refers to a combination. In principle, various types of polyester elastomers can be obtained by changing the types and proportions of dibasic acid, glycol, and polyester or polyether. For example, aromatic polyesters include polytetramethylene terephthalate, polyethylene terephthalate, etc., and aliphatic polyethers include polytetramethylene oxide, polyethylene oxide, etc.

Furthermore, by selecting a polyester elastomer as the TPE, it is possible to obtain an elastic hollow molded body having excellent oil resistance, strength and elongation properties, and excellent adhesion to S.PVC.

In addition, polyamide-based elastomers are multi-block copolymers that have a soft segment made mostly of aliphatic polyether, aliphatic polyester, or aliphatic polyether ester, and a hard segment made of polyamide. . 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 polycapramide, polyhexamethylene adipamide, polyhexamethylene sebamide, polyundecaneamide, polydodecanamide, etc., and aliphatic polyethers include polytetramethylene oxide, polyethylene oxide, etc. Examples include polyethylene adipate, polycaprolactone, polyethylene sepate, etc.

[Example 1] Hardness 50 (JISK6301A type), specific gravity 1.20
(ASTMD792), compression set 55% (JISK6301),
100 parts by weight of a plasticizer consisting of di-2-ethylhexyl phthalate (DOP) per 100 parts by weight of polyvinyl chloride with a melting point of 130°C (flow tester) and an average degree of polymerization of 2500.
Using an extruder with a screw length (L/D) of 24 mm and a screw diameter of 50 mm, S.PVC prepared by adding parts by weight was melt-kneaded at a set temperature of 160°C, while the hardness was 95,
Specific gravity 1.21, melting point 165℃, melt index
Using an extruder with a screw length (L/D) of 22 and a screw diameter of 50 mm, 0.5 g/10 min of polyester elastomer was melt-kneaded at a set temperature of 205°C.
Inside the extrusion die, S.PVC is used as the middle layer and polyester elastomer is bonded as the inner and outer layers, and the outer diameter is 40.
Coextruded as a cylindrical three-layer parison with an overall thickness of 2 mm and a wall thickness ratio of 10%, 80%, and 10% for the outer layer, middle layer, and inner layer, and the length is 200 mm as shown in Figure 1.
mm, bellows peak diameter 57mm, bellows trough diameter 44mm, average wall thickness
Duct A having a three-layer structure of 0.7 mm was manufactured by blow molding with compressed air of 7 kg/cm ² .

[Example 2] The same resin, extruder, and molding were used as in Example 1, except that the thickness ratios of the outer layer and the inner middle layer of the parison extruded in three layers were set to 25%, 50%, and 25%. A duct B having a three-layer structure was manufactured under the following conditions.

[Example 3] The S.PVC used in Example 1 was melt-kneaded in the same manner as in Example 1, and the hardness was 90, the specific gravity was 1.19, and the melting point was
Screw length (L/D) of polyurethane elastomer at 170℃, melt index 3g/10min
22. Using an extruder with a screw diameter of 40 mm, melt and knead at a set temperature of 185°C, and form S.PVC in the extrusion die.
is used as the middle layer, and polyurethane elastomer is bonded to the inner and outer layers, the outer diameter is 40 mm, the total thickness is 2 mm, and the wall thickness ratio of the outer layer, middle layer, and inner layer is 10%, 80%, and 10%.
Co-extruded as a cylindrical three-layer parison set at
Using the mold used in Example 1, a duct C as shown in FIG. 1 was manufactured by blow molding.

Duct C had excellent interlayer adhesive strength and could not be peeled off, had a high tensile strength of 3.3 Kg/mm ² , and was highly elastic. In addition, the hardness was measured after immersing it in JIS No. 1 oil at 30°C for 7 days, and almost no change in hardness was observed.

[Example 4] A S. PVC
were melt-kneaded in the same manner as in Example 1, and on the other hand, using an extruder with a screw length (L/D) of 22 and a screw diameter of 40 mm, polyamide elastomer with a hardness of 95 was mixed with S.PVC in the middle in an extrusion die. polyamide elastomer as the inner and outer layers, and the outer diameter
Co-extruded as a cylindrical three-layer parison with a thickness of 40 mm, total thickness of 2 mm, and a wall thickness ratio of outer layer, middle layer, and inner layer set to 10%, 80%, and 10%, using the mold used in Example 1, A duct D as shown in FIG. 1 was manufactured by blow molding.

Duct D had excellent interlayer adhesive strength and could not be peeled off, and had a high tensile strength of 2.5 kg/mm ² and was highly elastic. In addition, the hardness was measured after immersing it in JIS No. 1 oil at 30°C for 7 days, and almost no change in hardness was observed.

[Comparative Example 1] A single-layer duct E was produced using the S.PVC shown in Example 1 using the extruder and molding conditions also shown in the Example.

[Comparative Example 2] A single-layer duct F was produced using the polyester elastomer shown in Example 1 using the extruder and molding conditions also shown in Example 1.

Next, the results of comparing each of the above examples and each comparative example will be shown.

[Comparative Example 3] Parison extruded in three layers: outer layer, middle layer,
A duct G having a three-layer structure was manufactured using the same resin, extruder, and molding conditions as in Example 1, except that the wall thickness ratio of the inner layer was set to 30%, 40%, and 30%.

The walls of ducts A, B, C, and D obtained from Examples 1 to 4 and duct E obtained from Comparative Example 1 were partially cut into strips, and the tensile strength of each was measured. The results are shown in FIG. As shown in Figure 2, ducts A, B, C, and D, which are made of multiple layers of S.PVC and TPE of the present invention, have a tensile strength (JISK6301, tensile strength of 200 mm/min) compared to duct E, which is made of a single layer of S.PVC. ) has improved.

After filling the inside of duct B obtained from Example 2 and duct E obtained from Comparative Example 1 with grease (Etsuso, semi-fluid grease liquid), the openings at both ends were closed, and the changes in hardness over time were observed when left to stand naturally. The results are shown in FIG. As shown in Figure 3, duct E made of a single layer of S.PVC clearly showed a change in hardness, but duct B made of multiple layers of S.PVC and TPE of the present invention had almost no change in hardness and was flexible. It turned out to be excellent.

The wall thickness difference (thickness deviation) between the maximum wall thickness part and the minimum wall thickness part of ducts A and B obtained from Examples 1 and 2 and ducts F and G obtained from Comparative Examples 2 and 3 was determined, and Comparative Example 2 Examples 1 and 2 and Comparative Example 3 when the uneven thickness of is 100
Figure 4 shows the thickness unevenness ratio. As shown in Figure 4, as the S.PVC wall thickness ratio increases, the wall thickness deviation rate tends to decrease, and especially when the S.PVC wall thickness ratio is 50% or more, the molding defect rate is extremely low. A duct with uniform thickness can be obtained. The reason for this is thought to be that there is no drawdown of the parison and the parison itself can expand into a geared shape in good condition, resulting in a uniform wall thickness.

In the present invention, by molding an elastic hollow molded body with a three-layer structure of TPE/S.PVC/TPE and a specific wall thickness ratio, it can be easily bent and stretched with small force due to the flexibility of S.PVC. be able to. In addition, since the inner and outer layers are TPE layers, the inner and outer layers have high impact resistance, oil resistance, weather resistance, and tensile strength.Therefore, the molded product is less likely to break due to flying pebbles, and is also resistant to oils and fats such as grease. ozone,
No deterioration occurs when exposed to water, hot water, car wash detergents, etc. Furthermore, it is possible to mold a molded article with higher tensile strength than in the case of a single layer of S.PVC. Furthermore, by coating S.PVC with TPE,
S.PVC hardness change due to low temperature is suppressed by TPE,
There is little change in hardness due to low temperatures, and flexibility is maintained at low temperatures. It is also effective at high temperatures with little thermal deformation.

In particular, the middle layer S.PVC and the inner and outer layers are co-extruded with TPE to create a three-layer structure, and the wall thickness ratio of S.PVC is adjusted to the overall thickness.
An elastic hollow molded body having a composition of 50% or more and less than 97% has excellent flexibility and a uniform wall thickness.

If the wall thickness ratio of S.PVC is less than 50%, the drawdown when extruding the parison will be severe, the molding defect rate will be high, and it will not be possible to obtain an elastic hollow molded product with a stable and uniform wall thickness, and the flexibility will be poor. For example, there is a drawback that the sealing performance of the connecting portion between the elastic hollow molded body and other fitting parts is deteriorated.

100% modulus (the stress that acts on a molded product when it is stretched twice within the elastic deformation range) is used as a means of expressing flexibility, but S.
PVC wall thickness ratio is less than 50%, the desired 100%
Modulus cannot be obtained.

That is, in the case of S.PVC single layer, the 100% modulus is about 0.3Kg/ ^mm2 , and in the elastic hollow molded article of the present invention, it is at least 0.7Kg/ ^mm2 , preferably 0.5Kg/ ^mm2 or less, but this The elastic hollow molded article according to the invention is not particularly limited to the above 100% modulus range. On the other hand, the wall thickness ratio of S.PVC is
If it is 97% or more, the TPE layer will not be well-aligned in areas where the molded product has a high blowing ratio, resulting in loss of TPE properties, and also has the disadvantage that pinholes are likely to occur during molding, resulting in a high molding defect rate.

Note that elastic hollow molded bodies are at least S.PVC.
It is a general term for a molded product obtained by blow molding that is composed of three or more layers including a layer consisting of and TPE, and other resins can be laminated as long as the flexibility is not extremely impaired. Applications of elastic hollow molded bodies include ducts, hoses, dust boots, covers, etc. used in automobiles and other general industrial parts.

〔Effect of the invention〕

As described above, the present invention provides an elastic hollow molded body formed by blow molding, which has a multilayer structure including an outer layer made of a thermoplastic elastomer, an intermediate layer made of soft polyvinyl chloride, and an inner layer made of a thermoplastic elastomer. It is soft because the outer layer thickness T ₁ , the middle layer thickness T ₂ , and the inner layer thickness T ₃ are configured within the range of 0.5≦T ₂ / (T ₁ + T ₂ + T ₃ ) < 0.97. The problems of polyvinyl chloride are solved, and the following effects can be achieved.

In other words, soft polyvinyl chloride has excellent flexibility, but on the other hand, its hardness is highly temperature dependent, and its hardness changes significantly due to changes in environmental temperature.For example, in low temperature environments, its flexibility is significantly impaired; Plastic elastomers have low temperature dependence of hardness and have excellent impact resistance, oil resistance, and weather resistance, but on the other hand, they have poor flexibility and are difficult to bend and stretch with small force. In the elastic hollow molded article according to the present invention, the inner and outer layers of the layer made of soft polyvinyl chloride whose hardness is highly temperature dependent are covered with a thermoplastic elastomer whose hardness is low temperature dependent. The flexibility of the soft polyvinyl chloride is not impaired by changes in environmental temperature, and the characteristics of the elastic hollow molded body are not impaired by external influences. This prevents the molded product from cracking or breaking due to flying pebbles, for example, and prevents it from deteriorating due to oils such as grease, ozone, water, hot water, and detergents for car washes, and has excellent flexibility. can be maintained.

In addition, since both the inside and outside of the layer made of soft polyvinyl chloride are covered with a layer made of thermoplastic elastomer, the plasticizer added to the soft polyvinyl chloride will not be eluted to the outside.
Changes in hardness of soft polyvinyl chloride over time can be most effectively suppressed, thereby maintaining excellent flexibility. Therefore, there is no reduction in elasticity or flexibility caused by loss of flexibility, and furthermore, when used as an automobile part, for example,
The mounting part will not come off or generate noise due to vibrations and shocks when the car is running.

Furthermore, in the present invention, the thickness T ₁ of the outer layer 3
Since the thickness T ₂ of the intermediate layer 4 and the thickness T ₃ of the inner layer 2 are configured within the range of 0.5≦T/(T ₁ +T ₂ +T ₃ )<0.97, flexibility such as expansion and contraction is required. In an elastic hollow molded body, the characteristics of each layer can be best exhibited, excellent flexibility can be maintained, and an elastic hollow molded body with a uniform wall thickness can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of a bellows duct according to an embodiment of the present invention, and FIGS. 2, 3, and 4 are illustrations showing changes in tensile strength, hardness over time, and uniformity of wall thickness, respectively. It is a diagram.

Claims (1)

[Scope of Claims] 1. An elastic hollow molded body formed by blow molding, an outer layer made of a thermoplastic elastomer;
It has a multilayer structure consisting of an intermediate layer made of soft polyvinyl chloride and an inner layer made of thermoplastic elastomer, and the thickness of the outer layer T ₁ , the thickness T ₂ of the intermediate layer, and the thickness T ₃ of the inner layer are 0.5≦T. ₂ /(T ₁ +T ₂ +T ₃ )<0.97.