JPH07214587A - Surface hydrophilic synthetic resin molding - Google Patents

Abstract

PURPOSE:To improve the surface hyrophilic property of an injection molding by using a synthetic resin composition containing specific parts by weight of a surfactant for synthetic resin and also a die with a heat insulating layer on the wall surface. CONSTITUTION:When injection-molding a synthetic resin, a synthetic resin composition is prepared which contains 0.005 to 20 pts.wt. of one or two types min. of surfactant selected from among an anionic surfactant, a cationic surfactant, an amphoteric surfactant and a nonionic surfactant, for 100 pts.wt. of synthetic resin. Next, the die wall surface forming a die cavity in a main die consisting of a metal is coated in a thickness of 0.01 to 2mm by a heat insulating layer of a heat-resistant polymer with a thermal conductivity of 0.002cal/ cm.sea/ deg.C max. A highly surface hydrophilic synthetic resin injection molding is obtained using this die. In this case, the water droplet contact angle is 70 deg. max.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to parts for home electric appliances such as air conditioners, coolers and refrigerators, light electric appliances such as computers and liquid crystal display devices, and synthetic resin parts for electronic appliances.

[0002]

2. Description of the Related Art Air conditioners, chillers, refrigerators, etc. are generally widely used as general-purpose products and are economical in price. Injection molded articles of synthetic resin are widely used for parts of these light electric appliances and electronic appliances. They are required to have appropriate strength / elongation, rigidity, hardness, impact strength, and heat resistance, and are required to be economically molded. As a synthetic resin used for these, a styrene resin, that is, a polystyrene resin, a rubber-reinforced polystyrene, an AS resin, an ABS resin or the like is extremely excellent in terms of performance and price and is widely used.

Originally, when parts such as an air conditioner, a cool air blower, and a humidifier are injection-molded using a styrene resin which is a hydrophobic material, the surfaces of these parts are highly water repellent, so that water droplets are generated on the part surface. After adhering to the, the water droplets are blown off by blowing air, causing problems such as causing discomfort to surrounding objects and people, and causing damage. So far, this problem has been solved by applying a hydrophilic agent such as a surfactant to the injection molded product, but in recent years,
From the viewpoint of productivity, there is a strong demand for improvement in the surface hydrophilicity of molded products immediately after injection molding.

In response to this demand, attempts have been made to solve this problem by kneading a surfactant into a resin and then performing a molding process. However, in ordinary injection molding, the surfactant has an effect on the surface of the molded product. Since it is not distributed over time, it has not fully met this requirement. In order to improve this, it has been attempted to improve the hydrophilicity of the surface of the molded product by changing the injection molding conditions such as the injection pressure, the resin temperature and the mold temperature. The mold temperature has the greatest influence among these factors, and the higher the mold temperature, the more preferable. However, if the mold temperature is raised,
The cooling time required for the cooling and solidification of the plasticized resin is prolonged, and the molding efficiency is lowered. Therefore, there has been a demand for a method of improving the reproducibility of the mold surface without increasing the mold temperature and preventing the required cooling time from increasing even when the mold temperature is increased. There is also a method in which heating and cooling holes are attached to the mold and heating and cooling of the mold are repeated by alternately flowing a heat medium and a refrigerant, but this method also consumes a lot of heat, Cooling time becomes longer.

A method of improving mold surface reproducibility by coating a mold wall forming a mold cavity with a substance having a low thermal conductivity is disclosed in US Pat. No. 3,544,518 for injection molding. Also in extrusion blow molding, a method of coating the mold wall surface with a substance having a small thermal conductivity is disclosed in US Pat. No. 5,041,247.

[0006]

SUMMARY OF THE INVENTION There is a strong demand for synthetic resin moldings for parts such as light electric equipment and electronic equipment, which are economically molded by minimizing the increase in molding cycle time and have improved surface hydrophilicity. The present invention is the answer to this.

[0007]

As a result of studies to solve the above problems, the present invention has found that the surface hydrophilicity of a resin molded product molded by a specific molding method is extremely improved. That is, the present invention relates to (1) 100 parts by weight of a synthetic resin in an injection-molded product of a synthetic resin, containing an anionic surfactant, a cationic surfactant, an amphoteric surfactant and a nonionic surfactant. Using a synthetic resin composition containing 0.005 to 20 parts by weight of one or two or more kinds of surfactants selected from the above, (2) a mold for forming a mold cavity of a main mold made of metal The wall surface has a thermal conductivity of 0.002 ca.
(3) The contact angle of water droplets is 70 degrees or less, which is obtained by using a mold coated with a heat-insulating layer made of a heat-resistant polymer of 1 / cm · sec · ° C or less to a thickness of 0.01 to 2 mm It is a characteristic surface hydrophilic synthetic resin molding.

In the present invention, a molded product which is injection-molded by cooling the main mold temperature to a temperature lower than the softening temperature of the synthetic resin by 20 ° C. or less is preferable. What is particularly effective in the present invention is a part of a home electric appliance / electronic device in which a synthetic resin molded body includes a blower such as an air conditioner or a cool air blower as a constituent element. What is more effective in the present invention is a synthetic resin molded body in which the synthetic resin is a styrene synthetic resin.

The present invention will be described in detail below. The synthetic resin that can be used in the present invention is a thermoplastic resin that can be used in general injection molding. For example, styrene polymer, AB
S resin or its copolymer, olefin polymer such as polyethylene and polypropylene, modified polyphenylene ether resin, polyacetal resin, vinyl chloride polymer or its copolymer, polycarbonate, polyamide, polyester, etc. are generally used for injection molding. Thermoplastic resins can be used.

Styrene-based synthetic resins that can be particularly preferably used in the present invention include polystyrene resin, AS resin, etc., and rubber-reinforced polystyrene, ABS resin, AAS resin, MBS in which the rubber phase is distributed in an island shape in the resin phase. It is a resin or the like. The polystyrene resin is a styrene homopolymer and the AS resin is a styrene-acrylonitrile copolymer. In rubber-reinforced polystyrene, a rubber phase such as polybutadiene and SBR is dispersed in an island shape in a resin phase of a polymer mainly containing styrene. ABS resin is polybutadiene, S in the resin phase of the copolymer mainly composed of styrene and acrylonitrile.
The rubber phase such as BR is dispersed like islands. AAS resin is a resin in which the rubber phase of acrylic rubber is dispersed like islands in the resin phase of a copolymer mainly composed of styrene and acrylonitrile, and MBS resin is a copolymer mainly composed of styrene and methyl titaacrylate. Is a resin in which rubber is dispersed in an island shape in a resin phase consisting of.

Further, the present invention also includes blends mainly composed of these resins. For example, a rubber-reinforced polystyrene resin containing polyphenylene ether can be favorably used. Injection-molded products of these resins have a very good balance of performance and economic efficiency and are suitable for electric and electronic parts. Furthermore, when various reinforcing materials and various fillers are mixed with these resins, a particularly great effect is obtained. For example, one kind or two or more kinds of glass fiber, asbestos, calcium carbonate, talc, calcium sulfate, wood powder and the like can be blended with the above resin. Furthermore, in the present invention, in order to give a stone-tone or metallic appearance, the average particle size is 10 to 1000 μm.
A synthetic resin containing 0.002 to 20% by weight of particles having a gloss of m can be used particularly well.

The surfactant used in the present invention may be a carboxylic acid type, a sulfuric acid ester type, a sulfonic acid type, a phosphoric acid ester type or the like as an anionic surface active agent. As the amine salt, quaternary ammonium salt, pyridinium salt, etc., as the amphoteric surfactant, glycine type carboxylic acid, alanine type, imidazoline type, etc., and as the nonionic surfactant, polyoxyethylene type, polyvalent It is selected from alcohol type and other surfactants such as alkanolamides and polyethers. The total amount of surfactants added to the synthetic resin in the present invention is 0.005 to 20 with respect to 100 parts by weight of the synthetic resin.
Parts by weight. Preferably, the total surfactant is 0.0
It is 1 to 10 parts by weight. More preferably, the total amount of surfactant is 0.1 to 5 parts by weight.

In the present invention, the surface hydrophilicity of the resin is evaluated by the water drop contact angle. That is, a resin having a water droplet contact angle of 70 degrees or less is judged to have good surface hydrophilicity. A resin having a water drop contact angle of 60 degrees or less is preferable. More preferably, the resin has a water droplet contact angle of 50 degrees or less. In the present invention, a flat plate is cut out and conditioned for 72 hours in a temperature-controlled room at 23 ° C. and a relative humidity of 50%, and then a diameter of 1.5-2.
Gently drop a drop of 0 mm distilled water using a syringe, 1
After standing for 0 minutes, the surface contact angle is measured using a Kyowa Scientific Co. CA-S150 type contact angle meter.

The main mold material made of a metal described in the present invention is generally a synthetic resin such as iron or a steel material containing iron as a main component, aluminum or an alloy containing aluminum as a main component, a zinc alloy, and a beryllium-copper alloy. Includes metal molds used in molding. Particularly, steel materials can be used favorably. The heat-resistant polymer used for the heat insulating layer in the present invention is a heat-resistant polymer having a glass transition temperature of 150 ° C. or higher, preferably 190 ° C. or higher, and / or a melting point of 250 ° C. or higher, preferably 280 ° C. or higher. The heat conductivity of the heat resistant polymer is 0.002 ca.
It is 1 / cm · sec · ° C. or less, and that of a general polymer is less than this thermal conductivity. A tough polymer having a breaking elongation of 10% or more is preferable. The breaking elongation is measured according to ASTM D638, and the tensile speed at the time of measurement is 5 mm / min.

Polymers which can be favorably used as the heat insulating layer in the present invention are heat resistant polymers having an aromatic ring in the main chain, and various amorphous heat resistant polymers soluble in organic solvents, various polyimides and the like are favorably used. Can be used. As the non-crystalline heat resistant polymer, polysulfone, polyether sulfone, polyallyl sulfone, polyarylate, polyphenylene ether,
Examples thereof include polybenzimidazole. The repeating units of these typical heat resistant polymers are shown below.

[0016]

[Chemical 1]

[0017]

[Chemical 2]

[0018]

[Chemical 3]

[0019]

[Chemical 4]

[0020]

[Chemical 5]

Although there are various kinds of polyimide, a straight chain type high molecular weight polyimide can be favorably used. Generally, a straight chain type high molecular weight polyimide has a large breaking elongation and excellent durability.
Examples of linear high molecular weight polyimides that can be favorably used in the present invention are shown in Table 1. In addition, Tg is a glass transition temperature,
Also, n represents the number of repeating units.

[0022]

[Table 1]

The Tg of the linear polyimide differs depending on the constituents, and examples are shown in Tables 2 and 3. Tg is 15
Polymers at 0 ° C or higher can be used, preferably 190 ° C or higher, more preferably 230 ° C or higher.

[0024]

[Table 2]

[0025]

[Table 3]

Table 4 shows various soluble polyimides which can be favorably used in the present invention and can be dissolved in a solvent.

[0027]

[Table 4]

Injection molding has an economic value in that a molded product having a complicated shape can be obtained by molding once. In order to coat the surface of this complicated mold with a heat resistant polymer and firmly adhere it, a heat resistant polymer solution or / and a heat resistant polymer precursor solution is applied and then heated to obtain a heat resistant polymer. Most preferably, a coalescence is formed. Therefore, it is preferable that the heat resistant polymer or the heat resistant polymer precursor of the present invention can be dissolved in a solvent.

The above-mentioned non-crystalline heat-resistant polymer, soluble polyimide, or polyimide precursor is tetrahydrofuran, dimethylformamide, dimethylacetamide,
It is dissolved in various solvents such as N-methylpyrrolidone and used in the present invention. The linear polyimide precursor is synthesized, for example, by subjecting an aromatic diamine and an aromatic tetracarboxylic dianhydride to a ring-opening polyaddition reaction.

[0030]

[Chemical 6]

These polyimide precursors are heated to undergo a dehydration cyclization reaction to form a polyimide. The most preferable linear polyimide precursor is polyamic acid, and the repeating unit of a typical example thereof and the repeating unit of polyimide obtained by imidizing the same are shown below.

[0032]

[Chemical 7]

[0033]

[Chemical 8]

[0034]

[Chemical 9]

[0035]

[Chemical 10]

The polymer of the above polyimide precursor is N-
It is dissolved in a solvent such as methylpyrrolidone and applied on the wall surface of the mold. These heat-resistant polymer solution, or heat-resistant polymer precursor solution, to adjust the viscosity at the time of coating,
Additives for adjusting the surface tension of the solution and thixotropy can be added, and / or a small amount of additives for improving the adhesion to the mold can be added.

Regarding the heat resistant polymer used for the heat insulating layer,
Although the non-crystalline heat-resistant polymer and polyimide have been described, the present invention is basically not limited to these. Epoxy resin, silicone resin and the like having flexibility are usable depending on molding conditions. It is necessary that the adhesion between the heat-resistant polymer film of the present invention and the main mold is large, and at room temperature 0.5 kg / 10 mm width or more, preferably 0.8 k.
g / 10 mm width or more, more preferably 1 kg / 10 mm
It is more than the width. This is the peeling force when the adherent heat insulating layer is cut into a width of 10 mm and pulled at a speed of 20 mm / min in the direction perpendicular to the adhesive surface. Although the peeling force varies considerably depending on the measurement place and the number of times of measurement, it is important that the minimum value is large, and it is preferable that the peeling force is stable and large. The adhesion force described in the present invention is the minimum value of the adhesion force of the main part of the mold.

In order to further improve the surface smoothness of a thin layer of a heat insulating material such as polyimide, to further improve the scratch resistance of the surface, or to improve the releasability.
If necessary, another material thinner than about 1/10 of the thickness of the polyimide layer can be applied to the polyimide surface,
Included in the present invention. On the surface of synthetic resin sheets and molds,
A paint generally referred to as a hard coat, which is used to improve scratch resistance, can also be applied. For example, a thermosetting silicone-based hard coating agent, particularly a hard coating agent having excellent adhesion, which is obtained by blending a silicone-based hard coating agent with an epoxy-based substance, can be favorably used and is preferable for the present invention. It is also possible to apply a fluororesin or a silicone-based polymer in order to improve the releasability.

When injection molding is performed using a mold in which the mold wall forming the mold cavity of the main mold made of metal is covered with a heat insulating layer, the mold surface is heated by the heat of the injected synthetic resin itself. Molded. Therefore, it is possible to obtain the same effect as if the molding is performed by setting the temperature of the main mold high. In order to improve the mold surface reproducibility of the molded product and to improve the gloss of the molded product, the injected resin is in contact with the mold wall surface, and at least a small amount of pressure is applied to the resin to press it against the mold wall surface. It is necessary that the mold surface temperature is kept above the softening temperature of the resin only during the period. When the mold wall surface is covered with the heat insulation layer, the heat insulation effect of the heat insulation layer heats the mold surface by the heat of the injected resin, which improves the mold surface reproducibility and improves the gloss of the molded product.

The thickness of the heat insulating layer is appropriately selected within the range of 0.01 mm to 2 mm. Preferably 0.05 to 0.
It is 5 mm. Less than 0.01 mm, the effect is low and 2 m
It is not necessary to exceed m. A thickness (cm) / thermal conductivity (cal / cm · sec · ° C) value of 5 to 100 is particularly well suited for use in the present invention, and such a very narrow range is particularly effective. If it is smaller than the range of 5 to 100, the mold surface reproducibility tends to be poor, and if it is larger than this range, the cooling time inside the mold tends to be long, or the mirror-like coating of the low thermal conductive material tends to be difficult. Often occurs.

In the present invention, it is preferable that the temperature of the main mold is cooled to a temperature below the softening temperature of the thermoplastic resin by 20 ° C. or less before injection, and more preferably from the softening temperature to 2 ° C.
Molded at a temperature below 5 ° C and above room temperature. The softening temperature of the resin in the present invention is a temperature at which the synthetic resin can be easily deformed, and for the amorphous resin, the Vicat softening temperature (AST
MD1525), the heat distortion temperature (A
STM D648 load is 18.6 kg / cm @ 2), and for soft crystalline resin, the temperature is the heat distortion temperature (ASTM D648 load 4.6 kg / cm @ 2). The hard crystalline resin is a polyacetal resin, a polyamide resin or the like, and the soft crystalline resin is various polyethylenes,
It is polypropylene or the like.

According to the present invention, the mold surface is molded at a temperature not lower than the softening temperature of the synthetic resin for at least 0.1 seconds after the synthetic resin comes into contact with the mold surface. The temperature of the mold surface during injection molding changes with the temperature of the synthetic resin, the main mold, the heat insulation layer,
It can be calculated from specific heat, thermal conductivity, density, latent heat of crystallization, etc.
For example, ADINA and ADINAT (software developed at the Massachusetts Institute of Technology) are used to perform unsteady heat conduction analysis by the nonlinear finite element method. The values calculated concretely are shown in the figure.

FIGS. 1, 2 and 3 show the main mold temperature of 50.
Shown are the calculated values of the change in temperature distribution near the mold wall surface when injection molding was performed at 240 ° C. and the temperature of the rubber-reinforced polystyrene at 240 ° C. The numerical value of each curve in the figure shows the time (seconds) after the heated resin comes into contact with the cooled mold wall. The heating resin contacts the mold wall surface and is rapidly cooled, and the mold surface receives heat from the heating resin and rises in temperature. As shown in the figure, when the surface of the mold is covered with a heat insulating layer (polyimide), the temperature of the surface of the heat insulating layer in contact with the resin increases greatly and the temperature decreasing rate also decreases. When it is covered with a heat insulating layer, the mold surface temperature becomes higher as the time after the resin comes into contact with the mold wall becomes smaller, and the same effect as when the mold temperature is greatly increased by the heat insulating layer coating is obtained. It is obtained and there is little increase in the molded sultum. The fact that the time after the resin comes into contact with the mold wall is small corresponds to high injection speed and high-speed injection, and the number of seconds in the figure is the time from when the resin contacts the mold surface until high injection pressure is applied. Equivalent to.

In the present invention, the heat-insulating layer may cover the entire wall surface of the mold, or it may include the case where the molded product is locally covered only on the portion where surface hydrophilicity is required. When the molded product is to be coated only on the part where surface hydrophilicity is required, the metal mold is cut by the thickness of the heat insulating layer, and the heat insulating layer is formed on the cut part and polished. It is preferable that the surface of the mold and the surface of the heat insulating layer are combined to form a smooth mold surface.

[0045]

[Example] The following molds and materials are used. Main mold: Made of steel (S55C), has a 13-inch color TV housing mold cavity, the surface of the mold is mirror-like and hard chrome plated. There are four multi-point gates on the side of the mold cavity. Polyimide precursor and cured polyimide: Linear type high molecular weight polyimide precursor solution "Trenice # 3000"
(Manufactured by Toray Industries, Inc.). The performance of the cured polyimide is Tg
Is 300 ° C and thermal conductivity is 0.0005 cal / cm · s
ec · ° C, breaking elongation 60%. Polyimide-coated mold: A main mold is coated with a polyimide precursor solution, heated to 160 ° C. to partially imidize, then the coating and heating at 160 ° C. are repeated 5 times, and finally heated to 290 ° C. to obtain 100% imide. And surface polishing to 0.
Make a 1 mm thick polyimide coated mold.

A flat plate was cut out from this molded body and
After conditioning for 72 hours in a temperature-controlled room with a relative humidity of 50%, droplets of distilled water with a diameter of 1.5 to 2.0 mm were gently placed on the surface of the flat plate using a syringe under the same conditions, and left still for 10 minutes. Then, the surface contact angle is measured using a Kyowa Scientific Co., Ltd. CA-S150 type contact angle meter.

[0047]

[Example 1] Polystyrene resin "Asahi Kasei Polystyrene EXG11" as a styrene resin (Asahi Kasei Corporation)
2), sodium oleate 2% is added thereto, and granulated using a twin-screw extruder in which the cylinder temperature is set to 210 ° C. The obtained granulated product was heated at a cylinder temperature of 21.
Injection molding is carried out with the mold temperature set to 0 ° C. and 50 ° C. The surface contact angle of this molded body is 58 degrees.

[0048]

Example 2 Under the same molding conditions, "Asahi Kasei Polystyrene H-8672" added with 0.5% of sodium dodecylbenzenesulfonate is used for injection molding. The surface contact angle of this molded body is 62 degrees.

[0049]

Example 3 Injection molding is performed under the same molding conditions using "Asahi Kasei Polystyrene 680" to which 0.5% of stearylamine hydrochloride is added. The surface contact angle of this molding is 5
It is 8 degrees.

[0050]

[Example 4] "Styrac 18" to which 1.5% of polyoxyethylene octyl ether was added under the same molding conditions
Injection molding is performed using "0". The surface contact angle of this molded body is 52 degrees.

[0051]

[Example 5] "Asahi Kasei Polystyrene 190F" to which 0.5% of polyethylene laurate was added under the same molding conditions
Injection molding using. The surface contact angle of this molded body is 61 degrees.

[0052]

[Example 6] Injection molding is performed under the same molding conditions using "TENAC 5010" (manufactured by Asahi Kasei Co., Ltd.) to which 0.5% of polyethylene laurate is added. The surface contact angle of this molded body is 48 degrees.

[0053]

[Example 7] "Zylon 500" to which 1.5% of polyoxyethylene octyl ether was added under the same molding conditions
Injection molding is performed using "Z" (manufactured by Asahi Kasei Corp.). The surface contact angle of this molded body is 51 degrees.

[0054]

[Example 8] Under the same molding conditions, "Leona Resin 1300S" (manufactured by Asahi Kasei Corp.) added with 0.5% of polyethylene laurate is used for injection molding. The surface contact angle of this molded body is 30 degrees.

[0055]

EFFECTS OF THE INVENTION A synthetic resin molding having a good surface hydrophilicity can be obtained.

[Brief description of drawings]

FIG. 1 shows calculated values of changes in temperature distribution near the mold surface when a heated synthetic resin comes into contact with a cooled mold wall surface (without a heat insulating layer).

FIG. 2 shows calculated values of changes in temperature distribution near the mold surface when heated synthetic resin comes into contact with a cooled mold wall surface having a 0.1 mm heat insulating layer.

FIG. 3 shows calculated values of changes in temperature distribution near the mold surface when a heated synthetic resin comes into contact with a cooled mold wall surface having a 0.5 mm heat insulating layer.

Claims (1)

[Claims] 1. In an injection-molded product of a synthetic resin, (1) of 100 parts by weight of the synthetic resin, among anionic surfactant, cationic surfactant, amphoteric surfactant and nonionic surfactant. Using a synthetic resin composition containing 0.005 to 20 parts by weight of one or two or more kinds of surfactants selected from (2) a mold wall surface forming a mold cavity of a main mold made of metal Has a thermal conductivity of 0.002 cal / cm · s
0.01 for a heat insulation layer made of a heat-resistant polymer with a temperature below ec · ° C
Obtained by using a die coated to a thickness of ~ 2 mm, (3)
A surface hydrophilic synthetic resin molded product having a water drop contact angle of 70 degrees or less.