JPH054204B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a molded article of resin material. Structure of Conventional Examples and Problems Therein In the field of using unsaturated polyester resins, methods for producing gel-coated molded articles are known. In this method, a gel coat resin that is opaque in the transparent area and designed to prevent dripping is applied to the inner surface of a mold or resin mold (hereinafter referred to as the mold) by brushing, rolling, spraying, etc. 0.1
Apply to a thickness of ~1 mm. Then, once it has semi-cured, a base molding material made of a cheaper material, usually with a slightly different composition, is poured onto the gel coat (casting method), or a glass fiber mat or Backing is applied to the desired thickness by layering with cloth etc. (layering method) or spraying with cut glass fiber (chopped strands) (spray-up method). (buckling) and then left to harden at room temperature or under heating. With this method, the surface condition of the mold is faithfully transferred to the surface being made. That is, when the same gloss as the mold surface is obtained and the gel coat resin has transparency, it gives the product visual depth. If a gel coat is not applied, such gloss and visual effects cannot be obtained. Here, by using a gel cord resin with excellent hardness and chemical resistance, the surface properties of the product are improved and a product with even higher added value can be obtained. In other words, gel coats have great effects on both appearance and functionality of products. The above is an overview of the conventional technology. Unfortunately, however, within the scope of the prior art, the method of manufacturing gel-coated molded articles involves a large sacrifice in terms of work efficiency and man-hours. As a result, the advantages of the above-mentioned cutting angle are halved or offset by the economic disadvantages. This is because no matter how short the time required for semi-curing the gel coat described above is, it takes about 1
This is because it usually takes more than 2 hours, and in addition, the backing molding itself depends on a method that is extremely labor-intensive and time-consuming. However, this low productivity is primarily due to the fact that this method is carried out using molding temperatures (mold temperatures) ranging from room temperature to at most 60°C. More efficient molding methods developed in recent years, such as hot compression molding using bulk molding compounds BMC and sheet molding compounds SMC, or so-called "mechanical molding" methods such as injection molding and transfer molding. The reality is that the technology to combine the lining method with gel coat has not yet been established. One of the reasons for this is that all of the mechanical molding methods mentioned above have been developed mainly with the pursuit of economic efficiency by shortening the molding cycle, and in injection molding in particular, the products are often small. There is a contradiction in itself in combining the time-consuming gel coat method with such high-speed molding or molding of small, low-priced products. The second cause is
In such high-speed molding, the shearing force caused by the rapidly flowing base molding material destroys the gel coat coating on the mold surface, and in many cases wipes it out. However, there are many problems that are technically difficult to solve or have been considered almost impossible to solve, such as the fact that it is extremely difficult to uniformly apply gel coat resin to a heated mold. The point is that it exists. On the other hand, amidst the increasing social demand for ``more beautiful and more durable products at lower prices,'' there is a need to develop a manufacturing method for molded products with gel coat skins that solves the above-mentioned economic and technical problems. The demands are strong, and therefore, providing some kind of answer to these demands has now become an important task for engineers in the field. Purpose of the Invention The present invention has been made in view of the above circumstances, and is a method for producing a molded article with a gel coat skin, which overcomes the above-mentioned economical and technical problems that could not be addressed within the scope of the prior art. The purpose is to provide Structure of the Invention The present invention provides a method for manufacturing a molded article having a gel coat skin by the method described above using a heated mold in order to maintain high productivity similar to that of the mechanical molding method described above. The structure of this method will be described in detail below. (1) Composition of materials The gel coat resin and base molding material used in the present invention preferably both contain an unsaturated polyester resin and a curing agent thereof, and usually also contain several other components. Many of these ingredients are conventional in the art. The unsaturated polyester resin here is simply described in JIS K6900, and usually includes α-β ethylenically unsaturated dicarboxylic acids and saturated dicarboxylic acids used together if necessary (using their derivatives). In this specification, it refers to a polyester obtained by polycondensation reaction of polyester (sometimes used in polycondensate) and glycols, dissolved in a vinyl compound such as styrene, vinyltoluene, or methyl methacrylate, or an allyl compound such as diallyl phthalate. , also includes vinyl and/or allyl compound solutions in which epoxy acrylates or polyester acrylates are used in place of the polyesters, as they exhibit similar properties in various respects, according to the practice in this technical field; Of course, we take the position that it covers mixtures of these as well. Usually, gel coat resins are mainly made of the above-mentioned resins, with the addition of fine particles of silica, etc., to exhibit thixotropic flow characteristics (this has the effect of preventing dripping), and usually requires careful viscosity adjustment and defoaming operations. It is prepared by On the other hand, molding materials for substrates are made by blending the polyester resin with fillers, fibrous reinforcing agents, and other modifiers (e.g., low shrinkage agents), and as a result, the resin content is often 50% (by weight). ) below. Both of these resins for gel coats and molding materials for substrates are thermosetting by containing a curing agent as mentioned above, but especially for gel coat resins, it is also possible to use photocuring technology. This technology is also included within the scope of the present invention. In the present invention, not only the resin for the gel coat but also the molding material for the base body, only fluid ones are used. In the present invention, particularly devised materials are used among these materials, which will be described in detail below. First, in an embodiment of the present invention, the Sievers viscosity at a temperature of 25°C (nozzle length to diameter ratio 10, pressure 2.5Kg/cm ² ) is 1 to 150 poise, and the volume change rate due to curing is 3%. The following is true, and
Use a material that has a fast curing property with a curing time of not more than 15 minutes at 100°C and has storage stability at room temperature of more than 24 hours. The above description of the viscosity range means that the present invention uses a low-viscosity liquid material that is completely different from the material (usually solid or semi-hard) used in the conventional mechanical molding. Such a viscosity can be easily achieved by selecting the viscosity of the resin component and the type and amount of compounding agents such as fillers and fibrous reinforcing agents.
If the viscosity is below the above range, molding shrinkage will generally be large, causing cracks during molding or defects in the appearance of the molded product, and physical properties such as rigidity and heat resistance will also decrease; If it becomes more than that,
This is not preferable because it may destroy the semi-cured gel coat film, or cause it to be partially scraped off or cracked. Next, in the embodiment, the volume change rate of 3% or less due to curing corresponds to the value shown by so-called low-shrinkage type or non-shrinkage type materials among the materials normally used for the purpose. This means that it cannot be achieved without achieving extremely low shrinkage. Incidentally, even though compression molding that expands the material two-dimensionally shows zero dimensional change, that is, complete non-shrinkage, detailed measurements of the volumetric change show that the shrinkage is only 1 to 2%. It can be seen that this is occurring.
In the present invention, if such a low shrinkage material is not used as the molding material for the substrate, clutching or whitening will often occur during molding, and the product surface, that is, the gel coat surface, will usually have a satin finish, unevenness, and waves spreading from the injection port. This has an effect such as creating a pattern. However, techniques for reducing shrinkage are known, such as selection of polyester composition and type of vinyl monomer, addition of thermoplastic resin (in this case, vinyl monomer is additionally added at the same time). This can be achieved by adjusting the curing speed, etc. in an appropriate combination. The substrate molding materials of embodiments of the present invention are also formulated by known techniques to have a storage stability of at least 24 hours at room temperature (25° C.), which may include material containers, transport line piping, etc. The aim is to eliminate the hassle of daily cleaning and material loss, and it goes without saying that this will greatly help reduce product costs. Of course, it is desirable that these materials have storage stability for even longer periods of time. In addition, having storage stability in a specific place means
This means that even when a large amount of material is stored in a container, there is no significant qualitative change in the material within a certain period of time, and it can be used without any practical problems. The molding material for a substrate of the present invention is ideal in that it has the above-mentioned storage stability and hardens rapidly at elevated molding temperatures (described later). In other words, it has the above-mentioned rapid curing property, and without it, the economical merits which are the major object of the present invention cannot be utilized. In this specification, the curing time at 100°C refers to the set temperature (80°C) described in the "High temperature curing characteristics" section of JIS K6901.
and other reference temperatures by 20°C, and except that the curing agent is not specifically specified, it shall mean the "minimum curing time" obtained in accordance with the measurement method described in the same publication. In the present invention, a unique gel coat resin is also used. This feature is also very important and is the technical key of the present invention. That is,
In an embodiment of the present invention, the gel coat resin has a high viscosity (Bruckfield viscosity of thixotropic resin at 25°C according to JIS K6901, the same applies hereinafter) of 30 poise or more and a thixotropy (also JIS K6901) of 5 or more. , a high thixotropy type material that exhibits a curing speed at least equivalent to that of the base molding material is used. If the viscosity is above or below, even when it is semi-cured, it will not be able to resist the destructive action of the shearing force applied from the base molding material, and
It is also difficult to avoid dripping, repelling, etc. during coating due to the use of a heated mold (as a result, the viscosity of the resin applied to the mold is significantly reduced). Furthermore, if the thixotropy does not exhibit a high value as described above, it will not be possible to sufficiently avoid problems such as sagging and repelling as just described.
The viscosity of commonly used gel coat resin is 15
~30 poise and a thixotropy of 3.5 to 5, but in the embodiment of the present invention, a viscosity of 30 poise or more, especially 50 to 200 poise, and a thixotropy of 5 or more, especially 5.5 to 7 are used. Good results are obtained. Incidentally, the viscosity can be adjusted according to the method described above (Adjustment of viscosity of molding material for base body). On the other hand, regarding thixotropy, thixotropy imparting agents such as ultrafine anhydrous silica obtained by gas phase reaction method (this is the most commonly used), other fine particulate solids and fine fibrous substances (especially fiber length It can be adjusted by adding an appropriate amount of glass (typically milled fiber glass or whiskers) of 700 μm or less to the resin. In order to provide the above-mentioned high thixotropy, a significantly larger amount of thixotropy imparting agent is added to the gel coat resin of the present invention than in conventional resins, which is another feature of the present invention. That is, the content of the ultrafine anhydrous silica, which was conventionally generally 1 to 2% by weight, is as high as 2 to 6.5% by weight in the gel coat resin of the present invention, and furthermore, the content of the fine fibrous material is 2 to 6.5% by weight. By adding within a range not exceeding 25% by weight, the viscosity characteristics of the gel coat resin can be improved, cracks can be prevented during curing, and various physical properties can be improved after curing. If these thixotropy-imparting agents are added in large amounts exceeding the ranges mentioned herein, this is not preferable since it will have an adverse effect on coating workability and the finished appearance of the product. In addition, the viscosity of the gel coat resin can be sufficiently increased by adding only the thixotropic agent within the range shown here, so the addition of other fillers or thickeners is generally unnecessary. It is. In addition to these viscosity characteristics, it is extremely important for the gel coat resin of the present invention to exhibit rapid curing properties at the molding temperature. Normally, the curing of a gel coat film is delayed by a long time due to its thin film thickness, which is strongly protected by oxygen in the air, during which time the monomer components in the resin evaporate, and the release agent Unless a sufficiently fast curing material is used in the hardener system formulation, various physical properties,
Among other things, undesirable phenomena occur, such as a decrease in chemical resistance, and the formation of a beautiful and strong gel coat skin is hindered. Furthermore, if the curing of the gel coat is significantly delayed, there will be a significant temporal imbalance between the gel coat and the above-mentioned fast curing properties of the molding material for the substrate, and the characteristics of high-speed molding will be lost. Therefore, it is desired that the resin for gel coat has a fast curing property equivalent to that of the molding material for the substrate, preferably twice or more (compared under the same temperature conditions, of course). The upper limit of the curing rate is not particularly limited here, but it depends on the setting of storage stability, that is, pot life, and is self-limited. The base molding material and gel coat resin described above may naturally contain other components, such as various processing aids and modifiers. Particularly in the present invention, it is desirable to use a mold release agent, and fibrous reinforcing agents and the like also exhibit unexpected usefulness. (2) Manufacturing process In the present invention, the time factor is significantly modified compared to the conventional method, resulting in a significant improvement in work efficiency and productivity index. Each process, equipment, etc. will be explained step by step below. First, in the present invention, a mold is used, and in the embodiment, this mold is used in a state where the temperature is raised to 70 to 130°C. Mold temperature can of course be varied in a pattern throughout the molding cycle, but this generally results in losses in heat and time, which is undesirable. According to the present invention, when the mold temperature is maintained within the above range, manufacturing can be carried out with satisfactory productivity and quality. If the mold temperature is lower than 70°C, it will take time for the material (referring to both the gel coat resin and the molding material for the substrate) to harden, which deviates from the purpose of the present invention in terms of productivity; If it is too high, it will be difficult to apply the gel coat resin and uniform curing will be hindered, making it impossible to form a beautiful and strong gel coat skin. 80~120℃,
In particular, a preferable temperature range is 85 to 110°C in terms of productivity and quality assurance of the gel coat skin. Although it is possible to make materials that harden rapidly at temperatures below 70°C, such materials do not satisfy the above-mentioned storage stability conditions.
From this point of view, temperatures below 70°C cannot be used. In embodiments of the present invention, the gel coat is cured to a state suitable for injection or injection of the substrate molding compound, typically within 1 to 15 minutes after application, but injection or injection is carried out at an optimal time. The timing is very important, and if you remove it, you won't get a beautiful and strong gel coat. It is determined by trial and error method. Regarding the terms "injection" and "injection" used here, in the case of injection, a fixed amount of base molding material is injected into a mold under very low pressure or virtually no pressure. In injection, the material is injected into a closed mold under considerable pressure, typically several atmospheres, and then the material is under pressure for a period of time (the "holding" in traditional injection molding). pressure”, also known as “secondary pressure”)
can continue to be played. Therefore, in the injection method, the upper mold and the lower mold are strongly brought together and closed. On the other hand,
In the injection method, only an open mold, ie, a lower mold, is used, or an upper mold or just a plate is placed over the lower mold to provide a loose lid. In addition, in the method of the present invention, since a molding material for the substrate with low viscosity is used as described above, the injection pressure and secondary pressure are 2 to 20 Kg/cm ²
(as a gauge pressure) is sufficient, and the cost of molding machines and molds, as well as energy costs, are significantly lower than that of conventional injection molding, which uses high pressures of several hundred to several thousand kg/ ^cm2 . Benefits are found. However, it is not desirable for the material of the present invention to have a high glass fiber content as in the BMC and SMC, for example, it is practically possible to have a 3 mm chopped strand at 7% by weight, and a 6 mm chopped strand at 4% by weight. This is the highest content rate. Therefore, the method of the present invention is particularly advantageously applied to the production of thick-walled products with relatively low specific strength, such as artificial stone moldings. Either the injection method or the injection method is selected depending on the shape and characteristics of the desired product, and the latter is more advantageous in terms of product quality and productivity. Furthermore, the injection method has the advantage of being able to vary the pressure over a fairly wide range (for example, applying the static pressure of compressed gas directly to the material), giving it a greater degree of freedom in terms of materials and molding conditions. . As explained above, the method of the present invention is well included in the scope of injection molding or injection molding (which may also be referred to as reaction injection molding) of one-component thermosetting materials, and
It will be understood that this falls within the scope of high-speed molding or mechanical molding as described above. As an example, when employing injection molding methods, it is clear to those skilled in the art that, due to the material properties and molding conditions mentioned above, it is necessary to
Injection filling time of less than 40 seconds and total cycle time of less than 40 minutes (generally even less), even when trying to obtain products with dimensions of 3 m) and thick walls (e.g. 20-30 mm) Can be configured. still,
When in accordance with the present invention, it is generally preferable to apply an internal mold release agent to the material, e.g.
It is advantageous to carry out the molding process with the inclusion of % by weight of higher fatty acids or their metallic soaps. Such an internal mold release agent fully exhibits its performance in high temperature, high speed molding methods such as the method of the present invention, and does not cause any harm such as staining the mold or product surface. The mold release agent treatment normally performed in the industry involves applying the mold release agent and wiping it off (usually repeated twice), which requires considerable time and manpower, but according to the present invention, That can be easily omitted. Description of Examples In the following, parts and percentages related to the amount of each component
are all based on weight. This will be explained with reference to figures. Example 1 Orthophthalic unsaturated polyester, polyester thermoplastic resin and styrene monomer
100 parts of a resin component with a viscosity of approximately 100 centipoise (25°C) in a weight ratio of 33:7:60, 0.8 parts of benzoyl peroxide (hereinafter referred to as BPO), 0.15 parts of a mercaptan stabilizer, and stearin as a mold release agent. 3 parts of zinc oxide and 3 parts of zinc oxide were homogenized using a dope mixer A. on the other hand,
100 and 200 parts of calcium carbonate (NN#200, manufactured by Nitto Funka Kogyo Co., Ltd.) with an average particle size of about 15 μm and ankansuite (kansui #100, manufactured by the same company) with an average particle size of about 100 μm were screwed from tanks B and C, respectively. Transfer to blender E using conveyor D. Also, put 6 parts of 3mm glass fiber from tank F into blender E. Then, the materials from the dope mixer A are also put into the blender E, and these are kneaded.Finally, 1 part of a 50% methyl alcohol solution of a silane coupling agent having a mono(aminoethyl)aminopropyl group as a functional group is added to the blender E. In addition, the mixture was further kneaded to prepare a first base molding material. The viscosity of this product was approximately 30 poise (25°C), the curing time was 6.5 minutes (100°C), and the volume shrinkage rate when molded at 95°C was 0.8%. Next, 10 parts of styrene was added to 90 parts of bisphenolic unsaturated polyester resin (containing 40% styrene) to form a solution of 100 parts as a hardening agent.
0.8 parts of BPO and 0.3 parts of cobalt naphthenate (6% cobalt level) as an accelerator were added, and 3 parts and 4.5 parts of zinc stearate and ultrafine anhydrous silica were added and vacuum defoamed. ,viscosity
72 poise, thixotropy 5.9, curing time 3.3 minutes (100℃)
A first gel coat resin showing the following was obtained (J in the figure). As an example of a mold, the length and width are 350mm and 250mm, respectively.
Using a chrome-plated tray molding mold (H in the figure) having a thickness of 8.5 mm, molding was carried out with the mold heated to 95°C. That is, first, as shown in the figure, the lower mold I is taken out from the mold H to the right side, and here a gel coat is applied to the lower mold I using a spray method to form a gel coat film of about 0.35 mm, and then based on this. The mold was returned and squeezed with a force of 10 tons in the body G section, and after 3 minutes, the first base molding material in the blender E, which had been preheated to 40°C, was heated to an injection pressure of 6 kg/cm ²
The mixture was injected into the mold H for about 9 seconds, and after being left at the same temperature and pressure for another 10 minutes, the mold was opened and the molded product was taken out. This molded product has a beautiful and strong gel coat skin on the entire surface, and has a Barcol 934-1 hardness (JIS K6911) of 61 and a hardness of 5 at a temperature of 50℃.
% caustic soda aqueous solution immersion test (5 hours) showed almost no change including gloss. The surface was smooth, with no cracks or whitening, and had good gloss. still,
The molding material for the first base in blender E was left at room temperature, but it was still moldable two days later.
It was found to have sufficient storage stability. Example 2 In the base molding material of Example 1, Kansuiseki 200
160% of aluminum hydroxide [Higilite H-10 manufactured by Showa Light Metal Co., Ltd.] with an average particle size of about 60μm
In addition, the weight ratio of unsaturated polyester and styrene monomer was 30:63 to obtain a second base molding material with a viscosity of 14 poise, and in addition, in the gel coat resin of Example 1, only the amount of cobalt naphthenate was added. the second gel coat resin changed to 0.1 part;
And newly milled fiber glass with 3 parts of ultrafine anhydrous silica and an average fiber length of 20 μm.
A third gel coat resin having a viscosity of 45 poise and a thixotropy of 6 was obtained by adding 20 parts, and molding was carried out in accordance with Example 1 except that these resins were used in combination. The results are shown in Table 1 below. Comparative Example 1 In the base molding material of Example 1, by increasing calcium carbonate (NN#200) to 125 parts and glass fiber to 8 parts, the viscosity increased to 170 poise, but the volumetric shrinkage rate slightly decreased. decreased (0.6%)
A third base molding material was obtained. Example 1 was repeated using this material and the gel coat resin of Example 1, and the results shown in Table 1 were obtained. Comparative Example 2 In the gel coat resin of Example 1, only the particulate anhydrous silica was changed to 1.8 parts to obtain a fourth gel coat resin with a lower viscosity (viscosity of 9 poise, thixotropy of 4.4), and only this point was changed. Example 1 was repeated. The results are also shown in Table 1 below. Comparative Example 3 Example 1 was repeated using a fifth gel coat resin in which the cobalt naphthenate was replaced with a mercaptan stabilizer (0.4 parts added) and the curing time was 16 minutes. The results shown are obtained.
In Table 1, I for the base molding material and I for the gel coat resin mean the first base molding material and the first gel coat material, respectively.
etc.)

【table】

[Table] Effects of the Invention According to the present invention, a molded article having a beautiful and strong gel coat skin can be produced in an extremely short time compared to conventional methods. In addition, since it is a low-pressure, high-speed molding method, the molding machine can be simple, the mold can be simple and lightweight, and there is no need to manufacture a large number of molds as seen in conventional methods, so it has great economic advantages. Furthermore, the industrial utility value of this invention is extremely large due to the numerous effects that can be obtained, such as the advantage of using a storage-stable material and the good performance of the gel coat surface film that is formed using a high-temperature molding method. .

[Brief explanation of the drawing]

The figure is a configuration diagram showing an embodiment of the present invention. E...Blender, H...Mold (molding mold).

Claims (1)

[Scope of Claims] 1. A molded product in which a gel coat resin is applied to the inner surface of the cavity of a heated mold, and after the gel coat resin is cured or semi-cured, a base molding material is injected or injected into the cavity. manufacturing method. 2. As a molding material for the substrate, the Sievers viscosity at 25°C is 1 to 150 poise, the volume change rate upon curing is 3% or less, and the curing time at 100°C does not exceed 15 minutes. A method for producing a molded article according to claim 1, using a material having storage stability at room temperature. 3 As a gel coat resin, the Bruckfield viscosity at 25℃ is 30 poise or more and the thixotropy is 5.
The method for manufacturing a molded article according to claim 1, which uses a material that exhibits a curing rate at least equivalent to that of the base molding material. 4. A molded product according to claim 1 or 3, using a material containing 2 to 6.5% by weight of ultrafine anhydrous silica and 0 to 25% by weight of a fine fibrous substance as a gel coat resin. Production method. 5 Injection filling time of base molding material into mold
A method for manufacturing a molded article according to claim 1, wherein the manufacturing time is 40 seconds or less. 6. The method for producing a molded product according to claim 5, wherein the injection pressure is 2 to 20 Kg/cm ² (gauge pressure). 7. The method for manufacturing a molded article according to any one of claims 1 to 6, wherein the heating temperature of the mold is 70 to 130°C.