JP2017007313A - Blow molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blow molding method capable of realizing smooth introduction of a parison into a die cavity and free from the generation of demerits (such as deterioration in contamination and product quality and the change of device constitution) caused thereby.SOLUTION: Provided is a blow molding method where a cylindrical parison is inserted from an opening edge of the cavity of a closed die into a cavity and blow molding is performed. A lubricant is added to the parison. Further, a fibrous substance is added thereto. The lubricant is, e.g., fatty acid ester or fatty acid amide. The fibrous substance is, e.g., glass fiber. The molten resin of the parison is, e.g., polyamide resin. By blending lubricant-containing polyethylene pellet to polyamide resin pellet and melt-kneading the same, the lubricant is added to the parison.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a blow molding method in which a cylindrical parison is inserted into a cavity from a cavity opening end of a clamped mold and blow-molded.

  A so-called suction blow has been proposed as a technique for forming a hollow and long molded body such as a duct in an automobile engine. Suction blow is a technique in which a cylindrical parison is inserted into a cavity from a cavity opening end of a mold that is clamped and blow-molded, and has an advantage that a bent molded body can be easily formed.

  In the suction blow, it becomes impossible to form the parison when it is clogged in the mold cavity, so it is necessary to insert the parison smoothly. In particular, in the product bent portion, the parison surface and the mold cavity surface come into contact with each other, and the parison may be clogged in the mold and not reach the lower shutter. When such a phenomenon occurs, proper molding cannot be performed.

  As a general solution to this phenomenon, a method in which a liquid lubricant is applied or sprayed on the surface of a mold or sprayed on the molten parison itself has been studied. For example, in Patent Document 1, the lubricating liquid is poured into the inside and the outer periphery of the parison from the upper end opening, and the parison is smoothly guided into the cavity based on the flow action of the poured lubricating liquid. A blow molding method is disclosed in which after the lubricating liquid is discharged from the inside, each of the upper and lower ends of the parison is closed, pre-blowed into the parison, molded, cooled, and the molded product taken out.

  Alternatively, as another method, for example, US Pat. No. 6,057,052 introduces a plastically deformable extruded preform (parison) in the form of a plastic melt tube into a closed cavity and at least partially slides over the mold surface. In the suction-blow molding method, the Ra value of the cavity mold surface is set to 0.8 to 6.3 μm, and the Rz value is set to 6 to 40 μm, thereby reducing sliding friction with respect to the preform. It is described that it is planned.

JP-A-9-19956 Japanese Patent No. 4862299

  However, in the method of applying or spraying the liquid lubricant, the suction device for performing the parison suction is contaminated with the lubricant, it is necessary to prepare a separate device for supplying the lubricant, and the product surface There are problems such as contamination by lubricants. In addition, in the method of reducing the sliding friction by defining the surface roughness of the mold cavity surface, the surface property of the mold cavity surface is reflected on the product surface, and the surface property of the product is restricted. It will be.

  The present invention has been made in view of the above-described conventional situation, and can smoothly introduce the parison into the mold cavity, and the associated demerits (contamination and product quality deterioration, device configuration). It is an object of the present invention to provide a blow molding method that does not cause changes.

  In order to achieve the above-mentioned object, the blow molding method of the present invention is a blow molding method in which a cylindrical parison is inserted into a cavity from a cavity opening end of a clamped mold and blow-molded. It is characterized by adding a lubricant.

  By adding a lubricant to the parison, the slip of the parison is improved, and the parison is not clogged in the mold even in the bent mold cavity. At this time, the suction device for performing the parison suction is not contaminated, and it is not necessary to separately prepare a device for supplying the lubricant. The product surface is not contaminated with lubricant. There is no restriction on the surface properties of the mold cavity surface.

  In the blow molding method of the present invention, it is also effective to add a fibrous substance (glass fiber or the like) to the parison. The parison made of molten resin is soft and lacks rigidity. Therefore, it is easy to clog in the bent mold cavity. By adding the fibrous substance, the rigidity of the parison is increased, and the smooth insertion of the parison is realized in combination with the action of the lubricant.

  According to the present invention, smooth introduction of the parison into the mold cavity can be realized, and there are no disadvantages associated therewith. That is, it is possible to realize efficient blow molding (suction blow) without deteriorating product quality and without requiring new equipment investment.

It is a figure which shows the shaping | molding method by suction blow and shows the state before parison insertion. It is a figure which shows the shaping | molding method by suction blow and shows the insertion state of a parison.

  Hereinafter, embodiments of a blow molding method to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a blow molding apparatus for carrying out the blow molding method of the present embodiment. The blow molding method of the present embodiment is a so-called suction blow, and as shown in FIG. 1, a pair of molds 1 and 2 are clamped, and a parison 4 is inserted into a mold cavity 3 formed thereby. Then, the upper end and lower end of the parison 4 are sealed, and air is blown into the parison 4 to perform blow molding.

  The mold cavity 3 has a bent portion or the like according to the product shape, and the parison 4 is inserted into the mold cavity 3 from the upper open end 3 a that is the entrance of the mold cavity 3. FIG. 2 shows a state in which the parison 4 is inserted into the mold cavity 3.

  The parison 4 is formed by extruding a molten resin obtained by melting a thermoplastic resin into a cylindrical shape (tube shape) from a resin extrusion head. The thermoplastic resin to be used is not particularly limited, and any thermoplastic resin can be used as long as it can be molded. For example, in addition to polyolefin resins such as polyethylene resin and polypropylene resin, ethylene -Engineering plastics such as vinyl acetate copolymer, vinyl chloride resin, ABS resin (acrylonitrile-styrene-butadiene resin), polyamide resin, polystyrene resin, polyester resin, polycarbonate resin, and modified polyphenylene ether are suitable.

  Among these thermoplastic resins, for example, when a polyamide resin such as nylon (trade name) is used, the present invention is preferably applied. For example, polyolefin resin or the like is slippery and is not easily clogged in the mold cavity 3, whereas polyamide resin such as nylon is less slippery and is easily clogged in the mold cavity 3.

  In the blow molding method of this embodiment, when the parison 4 is formed, a lubricant is added in advance so that, for example, when a polyamide resin is used as the thermoplastic resin, the parison 4 can smoothly enter the mold cavity 3. Insertion is possible.

  As the lubricant, any commercially available one can be used. For example, any of hydrocarbon, fatty acid, fatty acid ester, fatty acid amide, and metal soap may be used. You may use together. Among these, polar compounds, that is, fatty acid ester-based and fatty acid amide-based lubricants are preferable. Examples of the fatty acid ester lubricant include monoglycerin oleate and diglycerin oleate. Examples of fatty acid amide-based lubricants include fatty acid amides such as stearic acid amide, oleic acid amide, and erucic acid amide, and alkylene fatty acid amides such as methylene bis stearic acid amide and ethylene bis stearic acid amide.

  In the parison 4, the addition amount of the lubricant is preferably 0.1% by mass to 1% by mass. If the addition amount of the lubricant is less than 0.1% by mass, the lubricating effect is not sufficiently exhibited, and the moldability of the parison 4 may be deteriorated. On the other hand, when the amount of the lubricant added exceeds 1% by mass, there is a risk that inconveniences such as deterioration of physical properties of the molded product may occur. In particular, when the parison 4 is formed of a polyamide resin and a lubricant is added to a polyethylene pellet having a high affinity to form a master batch and is added to the polyamide resin pellet which is a raw material resin, the amount of lubricant added increases in the polyamide resin. The ratio of the polyethylene resin increases, and the strength of the product may be reduced.

  The method of adding the lubricant to the parison 4 is arbitrary, but in order to uniformly disperse the lubricant, a master batch containing the lubricant is prepared, and this is blended into the raw material pellets and melted and kneaded. preferable. The master batch is a pellet containing a lubricant at a relatively high concentration, and this may be blended into the raw material pellet at a predetermined ratio.

  In this case, the resin material used for the masterbatch is preferably the same as the raw material pellet, but when the raw material pellet is, for example, a polyamide resin, the resin material of the masterbatch is polyethylene such as low density polyethylene (LDPE). It is preferable to use a resin or the like. That is, the lubricant is added to the parison by blending polyethylene pellets containing the lubricant with the polyamide resin pellets and melt-kneading them. When a fatty acid ester or a fatty acid amide is used as a lubricant, compatibility with a hydrophilic polyamide resin is poor and uniform dispersion is difficult. On the other hand, if a lipophilic polyethylene resin is used as the resin material of the masterbatch, the lubricant can be easily dispersed.

  It is preferable to add a fibrous substance to the parison 4. Examples of the fibrous material include glass fibers. By adding a fibrous substance to the parison 4, a certain degree of rigidity can be imparted to the flexible parison 4 using only a molten resin, and smooth insertion can be realized.

  The addition amount of the fibrous substance is arbitrary, but in order to obtain a predetermined effect, it is preferably about 15% by mass. In addition, since the addition of the fibrous substance affects the physical properties of the product, it is preferable to set the addition amount in consideration of the physical properties required for the product.

  In the blow molding method of the present invention, as described above, a lubricant or a fibrous substance is added to the parison so as to perform so-called suction blow, so that the parison can be smoothly smoothed without clogging in the mold cavity. Insertion is possible, and good moldability can be realized.

  As mentioned above, although embodiment which applied this invention has been described, this invention is not limited to this embodiment, and it cannot be overemphasized that a various change is possible in the range which does not deviate from the summary of this invention. .

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results.

Example 1
A master batch was prepared by adding a lubricant to low-density polyethylene (trade name: M1820, manufactured by Asahi Kasei Co., Ltd.), blended into raw material pellets, melted and kneaded, and extruded to form a parison. The extruded parison was inserted into the mold cavity, and suction blow molding was performed. The lubricant used is diglycerin oleate (liquid at normal temperature) which is a fatty acid ester. The net addition amount of lubricant (addition amount in Parison) is 0.15% by mass. As the raw material pellets, those obtained by adding 15% by mass of glass fiber to polyamide resin (trade name nylon 6) and pelletizing them were used.

The conditions for blow molding are as follows.
(1) Molded product size: Diameter 30mm x Length 400mm
(2) Molded product thickness: 0.5-2mm
(3) Parison injection speed: 22-23kg / h

Example 2
Suction blow was performed in the same manner as in Example 1 except that the amount of lubricant added was 0.30% by mass.

Example 3
A commercially available master batch (trade name ELB347, manufactured by Riken Vitamin Co., Ltd.) was used as the master batch, and suction blow was performed in the same manner as in Example 1. The lubricant is monoglycerin oleate (fatty acid ester) (melting point 63 to 67 ° C.), and the amount of lubricant added is 0.96% by mass.

Example 4
A commercially available master batch (trade name EXR070, manufactured by Riken Vitamin Co., Ltd.) was used as the master batch, and the suction blow was performed in the same manner as in Example 1. The lubricant is oleic acid amide (fatty acid amide) (melting point: 75 ° C.), and the amount of lubricant added is 0.38% by mass.

Example 5
A commercially available master batch (trade name ELM080 manufactured by Riken Vitamin Co., Ltd.) was used as the master batch, and the suction blow was performed in the same manner as in Example 1. Lubricant is erucic acid amide (fatty acid amide) (melting point 80 ° C.), and the amount of lubricant added is 0.29% by mass.

Example 6
Suction blow was performed in the same manner as in Example 1 except that no glass fiber was added to the raw material pellets.

Comparative Example 1
Suction blow was performed in the same manner as in Example 1 without using a masterbatch containing a lubricant (without adding a lubricant to the parison).

About each Example and comparative example more than evaluation, the presence or absence of generation | occurrence | production of clogging and the smoothness of parison insertion were evaluated. The results are shown in Table 1. In Table 1, o in the column of clogging indicates that no clogging has occurred, and x indicates that clogging has occurred. In the smoothness of parison insertion, ○ indicates that smooth insertion is possible, △ indicates that there is some difficulty in the insertion operation, and × indicates that insertion may not be possible due to clogging or the like. Respectively.

  As is apparent from Table 1, by adding a lubricant, clogging is eliminated and the moldability is good. Moreover, as apparent from a comparison between Example 6 and other examples, the operability of inserting a parison is improved by adding glass fiber.

1, 2 Mold 3 Mold cavity 4 Parison

Claims (7)

A blow molding method in which a cylindrical parison is inserted into the cavity from the cavity opening end of the mold clamped and blow molded,
A blow molding method comprising adding a lubricant to the parison.   The blow molding method according to claim 1, wherein a fibrous substance is further added to the parison.   The blow molding method according to claim 1 or 2, wherein the lubricant is at least one selected from fatty acid esters or fatty acid amides.   The blow molding method according to any one of claims 1 to 3, wherein an addition amount of the lubricant in the parison is 0.1 to 1% by mass.   The blow molding method according to any one of claims 1 to 4, wherein the fibrous substance is glass fiber.   The blow molding method according to any one of claims 1 to 5, wherein the parison is formed of a resin material mainly composed of a polyamide resin. The blow molding method according to claim 6, wherein the lubricant is added to the parison by blending polyethylene pellets containing the lubricant with the polyamide resin pellets and melt-kneading them.

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