JP2002096376A - Method for producing blow-molded article with pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a blow-molded article having a grain tone, etc., which can easily cope with an inexpensive apparatus, the change in shape of a resin and a molding, the change of a pattern, etc. SOLUTION: In the production of the blow-molded article with a pattern with the use of a molding raw material containing a molding base resin and a coloring agent master batch, flow resistance or deformation is given to the molten resin after a molding die 7 formed from a die 6 and a core 5. As the coloring agent master batch, a thermoplastic elastomer (1) the Vicat softening point of which is higher than the melting point or flow beginning temperature of the molding base resin, (2) the melting point or flow beginning temperature of which is higher by at least 20 deg.C than the melting point or flow beginning temperature of the molding base resin, and in which (3) MFR of the elastomer/ MFR of the molding base resin is at least 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a blow-molded article having a pattern appearance such as woodgrain, and more particularly, to a method for forming a pattern such as woodgrain using a molding raw material containing a specific colorant masterbatch. The present invention relates to a method for producing a blow molded product formed into a molded product.

[0002]

2. Description of the Related Art In recent years, products such as indoor furniture having a woodgrain or marble appearance have become widespread. In particular, such products are products having a film printed with a woodgrain or marble pattern attached thereto. Are circulating in large numbers. Although these patterns are artificially made to imitate natural objects, they are abstract and have a natural feeling, so they have become a boom as "healing" effects. In addition to products using these patterns printed films, products with woodgrain-like or marble-like appearance will also be manufactured by injection molding or extrusion molding, in order to obtain products with a thick feeling, Production by the blow molding method is also being considered.

As a method for producing a blow-molded article having a woodgrain-like or marble-like appearance, for example, Japanese Unexamined Patent Publication No.
JP-A-216233 discloses a toner composition comprising a thermoplastic resin (A) having a relatively low melting point and a thermoplastic resin (B) having a relatively high melting point which is colored in a different hue from that of the resin (A). A method of extruding a blend with at least one into a single-layer or multi-layer parison including the blend layer, and then blow molding, wherein the blend has a melting point of a thermoplastic resin (A) having a relatively low melting point or higher. In addition, kneading is performed at a temperature of 30 ° C. lower than the melting point of the thermoplastic resin (B) having a relatively high melting point, and then the temperature is reduced to the melting point of the thermoplastic resin (B) having a relatively high melting point or a temperature in the vicinity thereof. A method for producing a textured blow molded container extruded through a maintained die head has been proposed.

[0004] Japanese Patent Application Laid-Open No. 11-99557 discloses a molding material comprising a main resin (A) as a main component of a molded article and the following pattern forming material (B) for developing a pattern on the molded article. The pattern forming material (B) has a melt viscosity difference between (A) and (B) in the range of 100 to 10,000 cP (centipoise) at a temperature T at which the sagging time due to the weight of the main resin (A) is 10 seconds. A molding material using a resin in which the difference between the solubility parameter (SP value) of (A) and (B) is in the range of 0.2 to 4.0 has been proposed.

However, in these methods using resins having different melting points and melt viscosities, it is difficult to select a melting condition and a resin capable of forming a pattern such as a woodgrain pattern, and to control the temperature, and to form a stable pattern with good reproducibility. Is often difficult.

For this reason, as a new manufacturing method, Japanese Patent Application Laid-Open No. Hei 9-136348 discloses that a surface of a molten raw material obtained by mixing a color master batch into a compound containing a foaming or non-foaming agent of PVC resin is pinned by a circular die. A production method for generating turbulence and forming grain is disclosed.

As an improvement of this method, Japanese Patent Laid-Open Publication No.
Japanese Patent Application Laid-Open No. 1-48321 discloses a multilayer blow molding die, in which an outer layer resin inflow restricting means is provided at a position where an outer layer flow path joins an inner layer flow path, and a comb-shaped block is provided at a part in the circumferential direction or the entire circumference in the circumferential direction. The use of a multilayer die formed of a ring or a dam-shaped blocking ring in which a weir plate and projections are intermittently provided at regular intervals is disclosed.

[0008] That is, in each of the above methods, the flow of the molten resin composed of a plurality of molding materials is disturbed in the blow molding crosshead body to promote the appearance of patterns such as wood grain. It is intended to produce blow-molded articles having a wood grain pattern.

However, any of these means for disturbing the extruded flow of the molten resin includes:
This is for controlling the flow of the molten resin flow path between the mandrel and the ring die in the blow molding crosshead.
In addition, it is particularly necessary to use a multilayer molding die.

[0010] In the blow molding apparatus, the blow molding crosshead forms the basis of the blow molding machine connected to the end of the cylinder of the extrusion molding machine via an adapter. Therefore, equipping the blow molding crosshead body with a pin, a blocking ring, and the like means that the molding machine itself is a dedicated molding machine for forming patterns such as woodgrain.

In other words, it can be said that it is very difficult to replace the inner pin and the blocking ring in this part because of the components and the replacement time. Therefore, there is a problem that it is not possible to substantially consider the optimization of the pin and the blocking ring with respect to the change of the raw material resin and the change of the shape and size of the molded product. In addition, a stagnant portion is easily generated in the molten resin in this portion, and there is a possibility that the quality of the molded article is deteriorated due to decomposition of the resin. Therefore, there is a problem in using the same as the production of general blow-molded products, and from this point, it is considered that a dedicated machine must be used.

[0012]

SUMMARY OF THE INVENTION In a method for producing a molded article having a pattern such as woodgrain by a blow molding method,
Providing a method of producing patterned blow molded products that efficiently and stably develops patterns such as woodgraining, has low equipment costs, and can easily respond to changes in resin and molded product shapes and patterns. Is to do.

[0013]

In order to obtain a molded article having a pattern such as woodgrain by a blow molding method, the present inventor has proposed a colorant masterbatch, a molding base resin for developing a woodgrain, and molding conditions. We studied diligently. As a result, using a molding raw material including a colorant masterbatch, particularly a molding raw material composed of a combination of a coloring agent masterbatch having a specific relationship and a molding base resin, the molten resin flow formed by an easily replaceable die and core is used. By controlling the flow state in the road and controlling the deformation of the extruded parison, it has been found that a blow-molded product having many variations and a stable colored pattern appearance can be obtained. The present invention has been completed based on such knowledge.

That is, the present invention provides: (1) a parison obtained by melt-extruding a molding raw material containing a molding base resin (A) and a colorant masterbatch (B) from a molding die having an annular resin flow path; A method for producing a blow-molded article with a pattern by blowing a gas by sandwiching the resin with a mold to impart flow resistance or deformation to a molten resin after a molding die formed by a die and a core. (2) A parison obtained by melting and extruding a molding raw material containing a molding base resin (A) and a colorant masterbatch (B) from a molding die having an annular resin flow path is sandwiched by a mold and a gas is blown into the pattern. A method for producing a blow-molded article, the method comprising: providing a resistance to molten resin in a resin flow path in a molding die formed by a die and a core. (3) The method for producing a patterned blow-molded article according to (2), wherein the colorant masterbatch (B) contains the following thermoplastic elastomer. A thermoplastic elastomer having a Vicat softening point higher than the melting point or the flow start temperature of the molding base resin (A); Melt flow rate (MF
R) / Melt flow rate (MFR) of molding base resin
[Measurement under Measurement Conditions of Molded Base Resin] is 5 or more. (4) The method according to (2) or (3), wherein the molten resin in the resin flow path formed by the die and the core is extruded by applying a drawing resistance to the molten resin. (5) At least one or more resistance portions selected from uneven peaks, grooves, spirals, combs, and independent protrusions are provided on at least a part of the molten resin flow path of the die and / or the core to form a molten resin. The method for producing a patterned blow-molded article according to any one of (2) to (4), wherein resistance is imparted to the blow-molded article. (6) At least a part of the surface of the molten resin flow path of the die and / or the core is subjected to at least one type of surface processing selected from plating, roughening, resin processing, and coating processing (2). The method for producing a patterned blow-molded product according to any one of (1) to (5). (7) The method for producing a patterned blow-molded product according to any one of (2) to (6), wherein the annular shape of the core neck and the annular shape of the die lip portion are formed in non-similar shapes. (8) A parison obtained by melt-extruding a molding raw material including a molding base resin (A) and a colorant masterbatch (B) from a molding die having an annular resin flow path is sandwiched by a mold and a gas is blown into the pattern. In a method for producing a blow-molded article, multi-layer extrusion is performed using a molding raw material containing (A) and (B) as an outermost layer, and the extrusion speed of the outermost layer is made lower than the extrusion speed of a layer in contact with the outermost layer. Product manufacturing method. (9) The method for producing a patterned blow-molded article according to (8), wherein the colorant masterbatch (B) according to (3) is used. (10) A parison obtained by melting and extruding a molding raw material including a molding base resin (A) and a colorant masterbatch (B) from a molding die having an annular resin flow path is sandwiched by a mold, and a gas is blown into the pattern. A method for producing a blow-molded article, comprising: forming a patterned blow-molded article, wherein the parison is clamped by a mold before or after the parison is deformed before being clamped by the mold. (11) A method for producing a patterned blow-molded article according to (10) using the colorant masterbatch (B) according to (3).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION According to the method for producing a patterned blow molded article of the present invention, a molding raw material containing a molding base resin (A) and a colorant masterbatch (B) is melted from a molding die having an annular resin flow path. In a method of manufacturing a blow molded product with a pattern in which a parison obtained by extrusion is sandwiched by a mold and a gas is blown, an excellent pattern was developed by controlling mainly a molten resin after an extrusion die of a cross-head molten resin. This is to obtain a blow molded product. That is, this is a method for producing a patterned blow-molded product that imparts flow resistance or deformation to the molten resin after the molding die formed by the die and the core. Specifically, a method for imparting resistance to the molten resin in the resin flow path in the molding die formed by the die and the core, or before the parison is clamped by the mold, after the parison is deformed or while the metal is deformed. This is a method of clamping the mold.

The method for producing a blow-molded article with a pattern according to the present invention can be applied not only to a single layer but also to a multilayer blow. In the case of a multilayer, naturally, the molding base resin (A) and the colorant masterbatch (B) The layer made of the molding raw material containing is the outermost layer. Further, in this case, it is preferable that the extrusion speed of the outermost layer is lower than that of the adjacent layer.

The method for producing a blow-molded article with a pattern such as woodgrain according to the present invention uses a molding raw material comprising a molding base resin (A) and a colorant masterbatch (B), which constitute the main parts of the blow-molded article. It is to be blow molded. The colorant masterbatch (B) contains a colorant such as an inorganic pigment or an organic pigment for pattern expression, and is dispersed in the molding base resin (A) unevenly in a streak or the like. Thus, a pattern such as woodgrain is exhibited on the surface of the molded product.

The molding base resin (A) used in the present invention
There is no particular limitation, and a blow-moldable thermoplastic resin is used. Examples of the thermoplastic resin include polyolefin resins such as polypropylene resin and polyethylene resin, polyamide resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polynaphthalene terephthalate resin, and crystalline thermoplastic resins such as syndiotactic polystyrene resin. Is mentioned. Further, amorphous resins such as polystyrene resin, AS resin, rubber-modified polystyrene resin, ABS resin, polyvinyl chloride resin, and polycarbonate resin may be used. Among them, polypropylene resin, polyamide resin, ABS resin and the like are preferably used.

These molding base resins may be used, if necessary,
In order to improve the melting properties of thermoplastic resin, especially drawdown resistance, multiple resins are compounded, impact modifiers such as various elastomers are mixed, inorganic fillers such as talc, silica, glass fiber, oxidized An inhibitor, an ultraviolet absorber, a light stabilizer, a crystallization nucleating agent, a coloring agent, an antistatic agent, a plasticizer, and the like can be added.

The molding base resin (A) used in the present invention
And the melt flow properties of the colorant masterbatch (B)
In the case of a crystalline resin, the melting point can be specified, and in the case of an amorphous resin, the outflow start temperature can be specified. The relationship between the molding base resin (A) and the colorant masterbatch (B) is determined by the melting point or the outflow start temperature. Related to the group.

That is, based on the melt flow characteristics of the molding base resin (A), the colorant masterbatch (B) contains:
Those containing the following thermoplastic elastomers are preferably used. In addition, the thermoplastic elastomer includes a crystalline thermoplastic elastomer and an amorphous thermoplastic elastomer similarly to the molding base resin.

That is, the thermoplastic elastomer has a Vicat softening point higher than the melting point or the flow starting temperature of the molding base resin (A), and the melting point or the flow starting temperature is higher than the melting point or the melting flow starting temperature of the molding base resin (A). The melt flow rate of thermoplastic elastomer (MF
R) / Melt flow rate (MFR) of molding base resin
[Measurement under Measurement Conditions of Molded Base Resin] is 5 or more.

The colorant masterbatch contains a pigment exhibiting a pattern, particularly suitable for a grain pattern. This colorant masterbatch (hereinafter sometimes referred to as a pigment masterbatch) was used as a carrier resin containing a thermoplastic elastomer having the above-mentioned properties (and sometimes containing other thermoplastic resins). The reason for selecting such a thermoplastic elastomer, which has characteristics, will be described below.

Since the polymer having a low melting point (soft segment) and the polymer having a high melting point (hard segment) are continuous, mechanical characteristics and melting point can be adjusted by a combination of both. This makes it possible to adjust the softening temperature, melting point, outflow start temperature, and the like, which are important temperature parameters of the carrier resin in controlling the dispersion of the pigment, to the blow molding conditions.

Since it is a material having rubber-like properties, it is easily deformed even in a stage where flowability is not involved (a region exceeding the Vicat softening point and lower than the melting point or lower than the outflow starting temperature), and the dissolution of the pigment is suppressed. However, the master batch itself can be stretched or crushed appropriately. As a result, when the temperature exceeds the melting point or the outflow start temperature, the masterbatch is melted at a high speed without delay.

After the melting, since the viscosity is greatly reduced, the pigment is easily extruded together with the pigment on the surface layer side of the flow path, and the pigment easily flows, so that the flow pattern of the pigment is likely to appear. The thermoplastic elastomer that has been melted, stretched, and thinly deformed, when heated again, easily deforms and splits, and is dispersed in the molding base resin.
Recycling of burr etc. does not cause color disturbance.

The soft segment portion of the thermoplastic elastomer has high compatibility with the entire resin and contributes to the physical properties as a modifier. This is a characteristic that contributes to preventing a decrease in pinch-off strength and impact strength.

For these reasons, it is possible to finish a pigment masterbatch having a higher suitability for blow molding than a conventional pigment masterbatch exhibiting a colored pattern. Further, a process of making a colored pattern appear will be described in detail.

The Vicat softening point of the thermoplastic elastomer needs to be higher than the melting point of the molding base resin. This is because the molded base resin (A) and the pigment masterbatch (B) containing a thermoplastic elastomer as a carrier resin are charged into a hopper in a process of being transported in a solid state in a plasticizing cylinder in a large frictional or crushing force. Therefore, solid properties that maintain sufficient abrasion resistance and rigidity until the molding material melts beyond the melting point or the outflow starting temperature are required.

After passing through the solid transport section, the temperature in the cylinder gradually rises and exceeds the Vicat softening point of the thermoplastic elastomer, and the elastic strength of the thermoplastic elastomer starts to decrease. In the plasticization process, if the Vicat softening point of the thermoplastic elastomer is exceeded too early, the kneading force of the plasticizing screw causes the pigment masterbatch containing the thermoplastic elastomer to be finely divided, and the pigment itself is also released. .

As the plasticizing conditions for the molding material, the temperature set at the heater under the hopper is set to be equal to or lower than the Vicat softening point of the thermoplastic elastomer, and the temperature up to the outlet of the plasticizing cylinder is set to the melting point or the melting point or It is preferable to gradually increase the temperature in the temperature range up to the outflow start temperature.

Conversely, the thermoplastic elastomer contained in the pigment masterbatch has a higher Vicat softening point than the heater set point below the hopper and a higher melting point or outflow temperature than the exit temperature of the plasticizing cylinder. There is a need. Depending on the molding material and mechanical properties, this temperature condition range is wide, but as described above, thermoplastic elastomers can adjust these temperature properties, so pigment master batches can be manufactured as required. It is possible to do. The Vicat softening point is determined by ASTM
It is measured according to D 1525.

As for the melting temperature of the base resin and the thermoplastic elastomer, the melting point of the crystalline resin or the crystalline thermoplastic elastomer is defined as the melting temperature.
In the case of an amorphous resin or an amorphous thermoplastic elastomer, the melt-out temperature is not clear, so the flow-out start temperature is used. Generally, the melting point is raised to a temperature higher than the melting point at a heating rate of 20 ° C./min using a DSC7 differential scanning calorimeter manufactured by Perkin-Elmer Co., and then maintained for a certain period of time.
The temperature is lowered to room temperature at a rate of 20 minutes, and then the temperature is increased at a rate of 20 ° C./minute. In addition, the outflow starting temperature is generally defined as the outflow starting temperature measured using a Koka type flow tester. For example, using a nozzle having a diameter of 1 mm and a length of 5 mm, the temperature is raised at a rate of 5 ° C./min under 0.05 MPa, and the temperature at which the resin flows is measured.

Further, while the melting temperature is used as a guide, the suitability of the plasticized state is determined based on the melting state of the thermoplastic elastomer and the deformation state of the pigment master batch at the outlet of the plasticizing cylinder of the blow molding machine. Become. The melting point or outflow starting temperature of the thermoplastic elastomer is
It is preferable that the temperature is higher than the melting point of the base resin or the outflow start temperature by 20 ° C. or more when viewed from a general blow plasticization temperature profile.

In the present invention, even if the melting point or outflow starting temperature of the thermoplastic elastomer is higher than the melting point of the molding base resin, if the temperature difference is less than 20 ° C., it is difficult to obtain a clear grain pattern or stripe pattern. Inconvenience occurs.

The specific set temperature at the tip of the plasticizing extruder, that is, the most preferable temperature of the resin at the outlet of the plasticizing cylinder is as follows: When a crystalline thermoplastic elastomer is used as the carrier resin of the pigment master batch, -15) It is a temperature of about ℃ to -5 ° C.

With respect to the melt flow rate (MFR) of the thermoplastic elastomer, the molding base resin (A) used
(For example, polypropylene: measurement temperature 230 ° C., measurement load: 21.18 N)
The ratio of the MFR of the thermoplastic elastomer to the MFR of the molded base resin (the MFR of the thermoplastic elastomer / the MFR of the molded base resin) is 5 or more, preferably 10 or more, particularly preferably 20 or more. The upper limit of the MFR ratio is not limited, but if it is larger than necessary, the drawdown becomes large during molding. When the MFR ratio is less than 5, there is a problem that the pigment is hardly exposed or hardly stretched. The MFR is measured according to JIS K 7201.

The carrier resin in the pigment masterbatch is made of a thermoplastic elastomer having the above characteristics, and the thermoplastic elastomer is selected from polyester elastomers, polyamide elastomers, polyurethane elastomers, polyolefin elastomers and the like. .

For example, when the molding base resin (A) is a polyolefin resin such as polypropylene or polyethylene, a polyester elastomer having a PBT (polybutylene terephthalate) hard segment and a polyether soft segment is used. this is,
From a resin with a relatively high molding temperature such as polypropylene to a polyethylene with a low molding temperature, the Vicat softening point, melting point,
This is because the outflow start temperature and the melt viscosity can be adjusted according to the characteristics of the base resin.

Furthermore, inorganic pigments such as metal oxides and synthesized organic pigments have a higher affinity for polyester elastomers than non-polar molding materials such as polyolefin resins, so that they can be used even after they have been melted. Even if a slight kneading force or shearing force acts, the pigment is hardly transferred to the base resin side, and the pigment is hardly dispersed away from the carrier resin. Such a thermoplastic elastomer can be selected from many commercially available grades, but if necessary, can be newly synthesized. By properly selecting the carrier resin in this way, a pigment masterbatch having a clear colored pattern can be produced without lowering the blow moldability, particularly the drawdown performance.

The content of the thermoplastic elastomer in the colorant masterbatch is preferably from 20 to 90% by mass,
40-70 mass% is particularly preferred. The pigment component contained in the pigment master batch is preferably from 5 to 50% by mass,
0-40 mass% is particularly preferred. Further, a dye or the like is added in a complementary color. Further, kneadability at the time of producing a master batch can be improved by adding a polyolefin-based resin at 70% by mass or less as required.

When a patterned molded article is manufactured by the blow molding method of the present invention, the background (base) of the grain pattern is used.
It is preferable to add a base color pigment to the raw material for molding. The base color pigment may be added as it is, but is preferably added as a master batch. As the carrier resin of the master batch of the base color pigment, those which melt and flow below the melting point or the outflow starting temperature of the molded base resin are preferable, and examples thereof include low-density polyethylene, high-density polyethylene, linear low-density polyethylene, and polypropylene. . The addition amount of the base color pigment masterbatch is preferably 1 to 10% by mass of the molding raw material.
3% by weight is particularly preferred.

When the amount of the pigment masterbatch added for forming the pattern is 0.1 to 5% by mass in the molding raw material, a sufficiently satisfactory woodgrain appearance can be obtained. The addition amount of the pigment masterbatch for the appearance of the pattern varies depending on the use of the blow molded product and the difference in the hiding power of the base color pigment. Gives a sufficient grain feeling.

By performing general blow molding using the above-described pigment master batch, a good stripe pattern can be obtained. In particular, a clear wood grain feeling that has never been seen before as a wood grain blow product can be obtained. An epoch-making blow-molded product can be obtained with a resin having a high molding temperature that plasticizes at 200 ° C. or higher, such as polypropylene.

However, a product having such a streak pattern, particularly a product having a simple shape such as a plate shape, has a problem that a pattern change is small and only a monotonous straight grain appearance can be obtained. This is because there is a limit to giving a change to the pattern by this principle alone, because the colored pattern is striped along the resin extrusion flow, especially because the pigment is stretched using the shearing force near the flow channel wall surface. .

In addition, even when such a pigment masterbatch for expressing a pattern is used, not all of the added pigment effectively comes out of the surface of the molded product, and many pigments remain inside the resin even during extrusion. . The pigment that stays inside in this way is obscured by the base color pigment so as not to interfere with the pattern and is not used effectively, and if there is a high concentration of pigment inside, impact cracking and resin peeling at that part And so on.

Further, when an accumulator such as a direct accumulator (accumulator in a die) is located in the crosshead, the resin that has entered late has a sufficient amount of time when the prescribed amount of resin is reached without sufficient heating time. And is pushed out by the ring plunger. As a result, at the end of the parison, there is also a tendency for a shortage of insufficiently heated pigment pool to appear. Since such a portion is not preferable in appearance and also deteriorates the physical properties of the molded product, it is necessary to adjust the position of the mold so as to remove the molded product from the surface of the molded product. In the case of a side accumulator molding machine, such a phenomenon hardly occurs.

As described above, the pigment masterbatch for expressing a pattern using the thermoplastic resin containing the specific thermoplastic elastomer as a carrier resin has significantly improved blow molding suitability as compared with the conventional pigment masterbatch. Although the colored pattern was also good, it was necessary to add more appropriate blow molding means in order to increase the variation of the pattern and to solve the above-mentioned problems.

First, a means for preventing the pigment from remaining at a high concentration due to insufficient elongation will be provided. In the case of the present pattern master pigment masterbatch, the pigment is inherently difficult to separate from the carrier resin. Therefore, extracting the pigment is nothing but extracting the carrier resin. When the pigment masterbatch pellets melt deep inside the resin flow path, a considerable flow distance is required for the pigment portion to reach the surface. Furthermore, since the shearing force is smaller as the inside, it is hardly deformed, and it is easy to extrude the pigment pool.

In the present invention, as means for solving this problem, flow resistance or deformation is imparted to the molten resin after the molding die formed by the die and the core.
As a specific example, resistance is given to the molten resin in the resin flow path in the molding die formed by the die and the core. That is,
The thickness of the flow path of the molten resin flow path is narrowed down for a certain section, or the flow path is designed to be narrower than usual. In this manner, the carrier resin is easily deformed due to a large shear force acting thereon, and furthermore, the distance to the flow path wall surface can be shortened and the movement distance can be reduced. When narrowing the throttle or the flow path, the sharp throttle causes a rapid pressure change, which causes melt fracture and pulsation. In order to prevent these, the resin flow path composed of the ring die and the mandrel is gradually narrowed to have a gentle throttle gradient. In addition, if the extrusion speed is not reduced by the narrowed flow path, melt fracture and the like are likely to occur.

As another specific example, for example, uneven ridges, grooves, spirals, etc. may be formed on the molten resin flow path surface of the die and / or the core.
By providing a comb-like shape, independent projections, or the like, the flow of the resin can be changed, or the carrier resin can be directly deformed by being hooked. However, rapid flow changes are not preferred.

That is, since the pigment masterbatch for expressing the present pattern has better fluidity than the molding base resin, the pigment masterbatch is easily affected by a change in the flow, and the flow is disturbed and the dispersion is easy.
Grooves and spirals must be made gentle, and protrusions must be designed to reduce resistance. When a pigment is caught on a projection or the like, a weld mark is formed. Therefore, the protrusion is provided on the upstream side of the forming die, and a throttle is provided as much as possible on the downstream side so as to eliminate the weld mark.

In addition, a carrier resin containing a high concentration of an inorganic pigment such as a metal oxide is liable to be rubbed on the wall surface and has a lower wall resistance than a resin containing no ordinary inorganic substance, so that a shear force is applied to the carrier resin. There are times when it does not take. Metals and resins have different wettability (adhesion) depending on the combination or metal surface state, and the higher the wettability, the higher the wall resistance. For example, when plating is performed on the inner surface of the die without plating, the wettability with the resin becomes higher, and the carrier resin containing a high-concentration pigment easily spreads. In particular, plating of nickel, chromium, or the like is effective. Conversely, the inner surface of the die can be roughened to increase the flow resistance. It is also effective to apply a resin film so that the inner surface of the die is insulated.

In a flat die or the like, the die gap is adjusted so that the extrusion speed from the die is constant. That is, this is a case where the annular shape of the core neck portion and the annular shape of the die lip portion are non-similar. In the extrusion in which the reach distance from the die neck to the die exit is different, a flow velocity difference occurs in the circumferential direction of the die. Straight lines are deformed by this flow difference. When the streaks formed in this way are transferred to a plate-shaped mold or the like, a pattern that is not a linear stripe can be formed.

In the blow molding method, multilayer extrusion molding is often performed. In the case of forming a multilayer, if the outermost layer is a resin layer to which a colorant for pattern expression, that is, a pigment masterbatch is added, and the inner layer is made of the same material without adding a pigment, the outer layer has a thickness such that the inside can be concealed. As a result, molding can be performed with a low pigment cost. Furthermore, the thinner the thickness, the less the pigment stays in the interior, resulting in an efficient pattern, so that the pigment addition rate itself can be reduced.

In this molding, the extrusion speed on the inner layer side is made faster than the extrusion speed on the outer layer side, so that both sides of the die wall surface and the resin interface of the inner and outer layers act to extrude a single layer. As compared with the above, a clearer stripe pattern with more elongation is obtained. In such multi-layer molding, since the resin to be pinched and fused is mainly used as the inner layer material, the pinch portion is less likely to bite the high-concentration portion of the pigment, and a pinch-off strength that is particularly strong can be obtained. In this case, the difference between the extrusion speeds of the outermost layer and the inner layer is that the extrusion speed of the inner layer resin is 1.1 times or more, preferably 1.2 times or more the extrusion speed of the outer layer resin.

Another manufacturing method of the present invention is a manufacturing method in which an extruded parison is deformed before being clamped by a mold. When the parison is directly deformed, a pattern that is not a straight stripe is surely formed. Mechanically twisting and pulling the parison can be done with a relatively simple mechanism. For example, it is possible to insert the insertion rod from the lower side where the parison hangs down, and to perform deformation by lowering the parison by pushing up the parison from below using the operation of the blowing pipe. In a simpler method, the parison can be deformed by putting out an extra parison on the lower surface. If the pinch is blown up in such a state, a deformed stripe pattern can be surely formed.

Hereinafter, the method for producing a patterned blow molded product of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view schematically showing mainly a crosshead portion of a blow molding machine used for manufacturing a patterned blow molded product according to the present invention. 2 and 3 are longitudinal sectional views of a forming die (die changing portion). FIG. 4 is a longitudinal sectional view of a conventional molding die. FIG. 5 is a longitudinal sectional view for explaining the partial dimensions of the forming die.

FIG. 1 shows an example in which the blow head for blow molding has an accumulator in the head.
In the drawing, 1 is a mandrel, 2 is a ring die, 3 is a head body, 4 is a resin accumulator, 5 is a core, 6 is a die, 7 is a forming die (die changing part), 8
Denotes a ring plunger, 9 denotes a plasticizing unit, 10 denotes a molten resin flow path, 11 denotes a molten resin flow resistance part, 12 denotes a die lip, 13 denotes a parison, and 14 denotes a die gap controller.

In the first embodiment of the present invention, as shown in FIGS. 1 and 2, the head body 3 is formed by the mandrel 1 and the ring die 2 and melted and kneaded by the plasticizing unit 9. The resin is press-fitted into the crosshead, the ring plunger 8 rises, is stored in the resin accumulator 4, and is sent to the molding die through the annular molten resin flow path 10 due to the lowering of the ring plunger 8. .

At the lower part of the crosshead, a forming die (die changing part) 7 composed of a core 5 and a die 6 is detachably attached by bolts or screws (not shown). In the blow molding, the molten resin extruded by the ring plunger 8 is extruded from the die lip 12 through the molten resin flow path 10 to form a parison 13, and is sandwiched between a pair of molding dies (not shown).
The parison is shaped by blowing gas into 3 and the mold is opened after cooling to produce a patterned blow molded product.

The molten resin flow path 10 includes a ring die 2 and a die 6, a mandrel 10, and a vertically movable core 5. The thickness of the parison 13 is adjusted by moving the core 5 up and down by the die gap controller 14 to adjust the width of the die lip 12 at the die exit. Except for the die lip 12, there is no portion provided with a large resin resistance.

The melt of the colorant masterbatch (B) passing through such a structure (hereinafter referred to as a pigment) is sufficiently stretched if it can be transferred to the wall surface before reaching the die lip 12. If there is a pigment portion that has sunk inside, it is not stretched until it reaches the die lip portion 12 and narrows the flow path. The pigment part which has reached the die lip 12 and is extruded on the die wall surface begins to be deformed by receiving a large shearing force, but is extruded without being stretched sufficiently without being stretched sufficiently due to a short shearing distance. Is done. In such a pigment portion, the pigment itself protruding from the resin is observed, and in some cases, puncturing is performed without stretching during blow-up.

FIG. 2 is a longitudinal sectional view of a forming die (die changing portion) in which a throttle resistance is provided in a resin flow path. That is,
In order to extrude the pigment portion extruded at a high concentration described with reference to FIG.
An example is shown in which the flow path width between the die 6a and the core 5 is gradually narrowed in the die lip direction so as to be a resistance portion in the molten resin, and the core neck portion 5b is a throttle resistance portion.

The rapid drawing makes it difficult to extrude the parison stably due to the shear memory effect of the molten resin. Therefore, it is good to provide it gently from the upstream side which flows into a forming die part. By giving a gradient to the flow path width in this way, the shear force acting on the pigment portion can be increased without giving a sudden change in the flow. In this case, if the flow path is too narrow, the pigment part is excessively deformed in the horizontal direction,
It may be difficult to form a good line pattern. Usually, it is appropriate to reduce the size to 1 to 5 times the pellet size of the pigment master batch just before the entrance of the die lip 12.

FIG. 3 shows another forming die for the drawing resistance portion, and shows an example in which the change of the drawing is formed gently. That is, the narrowing of the narrow channel is shorter than in the case of FIG. 2, and the molding die is more excellent.

FIG. 4 shows a general molding die. Even if this molding die is used, a sufficiently practical pattern can be provided depending on the selection of the colorant master batch. As the width of control and molding conditions narrows,
In some cases, it is difficult to sufficiently express the pattern.

As another example of imparting resistance to the molten resin, in the general molding die shown in FIG. 4, the surface of the core 5 and / or the die 6, preferably the surface of the die 6, has uneven peaks,
At least one kind of groove, spiral, comb-like or independent protrusion can be provided. This example is effective in forcibly pulling out the pigment portion inside, or streaking the welded portion formed of the convex portion with the pigment interposed therebetween.

If the mounting projection has a large flow resistance, the pigment is easily dispersed and the pattern is likely to be disturbed. Therefore, the structure is such that the pigment is caught without causing a large flow resistance of the resin. The wing-shaped comb structure parallel to the resin flow direction has the lowest resistance. The processing of the protruding portion may be performed by cutting, embedding a part, or separating parts and screwing.

Since the weld is formed when the resin passes through the convex portion, the convex portion and the like are provided on the die 6a, which is the upstream portion, as much as possible so that the weld can be eliminated on the downstream side. To increase the pressure. The shape of the throttle portion as the throttle portion may be a whole annular shape or a partial shape. The formation of such irregularities can of course be performed in combination with the cases shown in FIGS.

As another specific example, the core 5 is reduced at the front end side so as to have a converge die shape in which resistance is given to the molten resin. In this case, since the leading end of the molding die is narrowed more than the intermediate portion, the pressure of the resin is further increased and the density is increased, and the repair and elimination of the weld marks are more reliably performed. Also, if the drawing ratio and the drawing angle at the tip of the forming die are increased, the parison folding phenomenon (flare phenomenon) occurs due to the shearing memory effect of the resin. If this phenomenon is large, the parison becomes unstable, but if the flare is a certain degree, it has the effect of deforming the streaks, and the appearance of a deformed stripe pattern other than a linear stripe pattern can be expected.

In contrast to a general molding die in which the diameter of the annular resin flow path changes in a similar manner in the flow direction of the molten resin to reach the die lip, another example is as follows. That is, at least the lower end of the core 5b and the die 6b and the lower end of the core 5c and the die 6c, that is, the annular shape of the core neck and the annular shape of the die lip are non-similar.

For example, there is a flat die in which the annular shape of the die lip portion is elliptical. Even with a parison extruded through such a die lip, the extrusion speed of each part of the outlet is designed to be the same. In a die that extrudes a flat parison in this way, a velocity component is also generated in the circumferential direction, and as a result, the colored pattern of the extruded parison changes in the outer peripheral direction, and the width and spacing of the colored streaks are different. Comes out. Such a flat die is often used for forming a wide plate-like product, and even a plate-like molded product is formed with a changeable pattern, and is particularly suitable for a wood grain-like appearance.

The means for imparting resistance to the melt-flowable resin in the core and the die to stabilize and clarify the stripe pattern or to change the pattern has been described by way of specific examples. In addition to these methods, in the case of adding the pigment masterbatch (B) which is indispensable in the present invention, many means can be devised as long as a blow molding method for producing a colored pattern such as a woodgrain appearance. However, the example shown here is only a part.

The patterned blow-molded article obtained by the present invention comprises:
As long as blow molding is possible, the shape is arbitrary, and any shape can be manufactured from a container shape to a plate shape and various shapes based on the application. Also, on the surface of the molded product, various patterns including a wood grain pattern are satisfactorily formed,
It can be commercialized without secondary processing such as surface treatment such as painting again, and is extremely suitable as a molded product used for various applications.

For example, detergents, cosmetics, chemicals, containers such as cooler boxes, gardening supplies such as flowerpots and planters, desk tops, bed tops / bottoms, sideboards, shelves, storage boxes, tables and other furniture. Building materials such as ceiling boards, partition boards, floorboards, window frames, doors, benches, armrests, handrails, handles, vanity doors, bath lids, bath side panels, toilet seats, shower heads, bath counters, bathroom walls, etc. Sanitary products, air spoilers, doors, bumpers, sunroofs, instrument panels, armrests, headrests, wheel caps, console boxes,
Automotive parts such as glove boxes and trunk boards,
Container, musical instrument case, attache case, printer,
Surfboards, wind surfing, such as copiers, air conditioners, transport supplies such as TV stands, and home appliance housings.
Sports and leisure equipment such as snowboards, outdoor tables, camping equipment, and playground equipment can be exemplified.

[0077]

The following are specific examples of molding experiments, but are not limited to these examples.

Molding Experiment 1 This is a molding experiment in which a drawing resistance is given, which is an example of the method for producing a patterned blow molded product of the present invention. Molding base resin (A)
As polypropylene resin [Idemitsu Petrochemical Co., Ltd. E
150 GK, melting point: 160 ° C., MFR: 0.6 g / 10
Min.) = 100 parts by mass, as a colorant masterbatch (B), a color pigment masterbatch for wood grain “polyester-based elastomer [Duprene P2 manufactured by Toyobo Co., Ltd.]
80B, melting point: 218 ° C, Piccat softening point: 199 ° C,
MFR: 13 g / 10 min] = 45% by mass, low-density polyethylene = 20% by mass, dark brown inorganic pigment = 30% by mass,
Modified SEBS [ToughTech M1913 manufactured by Asahi Kasei Corporation] =
5% by mass "= 0.5 parts by mass, and 2 parts by mass of a LD-based coloring pigment master batch (beige) for molding base material = 2 parts by mass.

As a blow molding machine, a V8 type blow molding machine (ring plunger type accumulator system) manufactured by Nippon Steel Works, Ltd. was used. Using the molding dies shown in FIGS. 2, 3 and 4, blow molding was performed using a 1.8-liter flat rectangular bottle molding die to produce a blow molded product with a pattern.

The features of each forming die are as follows. The dimensions of each part are shown corresponding to the reference numerals in FIG. FIG. 2: a> b, c−b = 6 mm, d = e = 10 mm FIG. 3: a = b, c−b = 6 mm, d = 10 mm, e = 5
mm FIG. 4: a = b, c−b = 10 mm, d = e = 10 mm Molding conditions are extruder cylinder temperature: 180 to 210
° C, the temperature of the head body and the forming die: 220 ° C, and the extrusion amount was 220 grams. As a result, the stripes were clear in all of FIGS. 2, 3 and 4, but in FIG. 4, a high-concentration pigment part was generated at the end of the parison, and a part was included in the molded article.
In FIG. 2, the high-concentration pigment portion was reduced, and there was no high-concentration pigment portion included in the molded product. However, the stripes were slightly disturbed, and a part of the pigment was raised on the surface of the molded product. In FIG. 3, there was no pigment portion of high concentration, the stripes were clear and the elongation was good, and the woodgrain feeling was the best.

Molding Example 2 Using a two-layer blow molding machine, the molding material used in Molding Example 1 was used as the outer layer molding material, and the base resin polypropylene was used as the inner layer. The parison layer ratio (interior / outer layer = 2, flow rate ratio 1.2. The obtained bottle was
Vertical stripes were clearly formed, and insufficient elongation did not occur.

Molding Example 3 In Molding Example 1, using the molding die shown in FIG. 4, the extrusion amount was increased to 240 g while the gap amount of the die lip was kept the same, and the parison was elongated until the parison hit the blowout pin opening and deformed. And blow-up without pre-blow. This was performed for 20 consecutive shots.
As a result, the product was taken out with some burrs protruding from the mold, but no defective product was formed. Wavy stripes were generated in all the products, and the appearance of the product was significantly different from the straight-grained woodgrain appearance.

[0083]

According to the present invention, even when molded under general blow molding conditions, a pattern such as woodgrain is clearly developed, and it is easy to control the application of flow resistance to the molten resin. Further, the flow resistance is applied not by the die body of the crosshead but by the device of the die exchanging unit, so that it is easy to cope with various patterns and the cost is not required. In particular, when a molding raw material composed of a combination of a specific colorant masterbatch and a base resin is used, a blow molded article excellent in pattern expression such as a more excellent grain pattern can be manufactured by combining a few molding means. In addition, even with a simple operation of deforming the parison before holding the mold, an excellent pattern can be developed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a crosshead portion which is a main part of a blow molding machine used in a method for producing a patterned blow molded product of the present invention.

FIG. 2 is a longitudinal sectional view of a forming die (die changing portion) of the present invention.

FIG. 3 is a longitudinal sectional view of a forming die (die changing portion) of the present invention.

FIG. 4 is a longitudinal sectional view of a conventional forming die (die changing portion).

FIG. 5 is a schematic longitudinal sectional view for explaining a partial dimension of a forming die.

[Explanation of symbols]

 1: Mandrel 2: Ring die 3: Head main body 4: Resin accumulator 5: Core 6: Dice 7: Molding die (die exchange part) 8: Ring plunger 9: Plasticizing unit 10: Molten resin flow path 11: Molten resin flow resistance section 12: Die lip 13: Parison 14: Die gap controller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08J 5/00 C08J 5/00 C08L 101/00 C08L 101/00 // B29K 101: 12 B29K 101: 12 B29L 7:00 B29L 7:00 31:44 31:44 F term (reference) 4F070 AA06 AA13 AA15 AA18 AA47 AA71 AB08 AB09 AB11 AB16 AE04 FA17 FB03 4F071 AA01 AA02 AA10 AA84 AA85 AA88 AE09 AH03 AH07 AH19 BB13 BC08 AF08 BC08 AF08 AJ09 LA01 LB01 LD16 LG06 LG22 LG26 LH17 LH18 4J002 BB012 BB021 BB032 BB052 BB111 BB122 BC031 BC061 BD041 BN141 BN151 CF002 CF061 CF071 CF081 CF102 CG001 CK022 CL001 CL002 FD010 FD096 GC00 GL00

Claims (11)

[Claims] 1. A parison obtained by melting and extruding a molding raw material including a molding base resin (A) and a colorant masterbatch (B) from a molding die having an annular resin flow path, and holding the parison in a mold to blow gas. A method for producing a patterned blow-molded article, the method comprising: providing a flow resistance or deformation to a molten resin after a molding die formed by a die and a core. 2. A parison obtained by melting and extruding a molding raw material containing a molding base resin (A) and a colorant masterbatch (B) from a molding die having an annular resin flow path is sandwiched between molds to blow gas. A method for producing a patterned blow-molded article, comprising: providing a resistance to molten resin in a resin flow path in a molding die formed by a die and a core. 3. The method for producing a patterned blow-molded article according to claim 2, wherein the colorant masterbatch (B) contains the following thermoplastic elastomer. A thermoplastic elastomer having a Vicat softening point higher than the melting point or the flow start temperature of the molding base resin (A); Melt flow rate (MF
R) / Melt flow rate (MFR) of molding base resin
[Measurement under Measurement Conditions of Molded Base Resin] is 5 or more. 4. The method for producing a blow-molded article with a pattern according to claim 2, wherein the molten resin in the resin flow path formed by the die and the core is extruded with a drawing resistance. 5. At least a portion of a molten resin flow path of a die and / or a core is provided with at least one or more resistive portions selected from uneven peaks, grooves, spirals, comb teeth, and independent protrusions. The method for producing a patterned blow-molded article according to any one of claims 2 to 4, wherein resistance is imparted to the molten resin. 6. At least a part of a surface of a molten resin flow path of a die and / or a core is subjected to at least one kind of surface processing selected from plating, roughening, resin processing, and coating processing. A method for producing a patterned blow-molded product according to any one of claims 2 to 5. 7. The method for producing a patterned blow-molded product according to claim 2, wherein the annular shape of the core neck and the annular shape of the die lip portion are formed in non-similar shapes. 8. A parison obtained by melt-extruding a molding raw material including a molding base resin (A) and a colorant masterbatch (B) from a molding die having an annular resin flow path, and holding a parison in a mold to blow gas. In the method for producing a patterned blow-molded product, a molding raw material containing (A) and (B) is extruded as a multi-layer as an outermost layer, and the extruding speed of the outermost layer is made lower than the extruding speed of a layer in contact with the outermost layer. Manufacturing method of blow molded products. 9. The method according to claim 8, wherein the colorant masterbatch (B) is used. 10. A parison obtained by melting and extruding a molding raw material including a molding base resin (A) and a colorant masterbatch (B) from a molding die having an annular resin flow path, and holding the parison in a mold to blow gas. A method for producing a patterned blow-molded article, wherein the parison is clamped by a mold after or after the parison is deformed before the parison is clamped by the mold. 11. The method for producing a patterned blow-molded article according to claim 10, wherein the colorant masterbatch (B) according to claim 3 is used.