JP2006063126A - Injection molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molded product using a resin excellent in precision moldability and heat decomposition resistance. <P>SOLUTION: The injection molded product is produced by using a resin obtained by hydrogenating aromatic rings of a copolymer having 0.25-4.0 molar ratio (A/B) of a structural unit (A mole) originating from a (meth)acrylic ester monomer over a structural unit (B mole) originating from an aromatic vinyl monomer in the structural units obtained by polymerizing a monomer composition containing the (meth)acrylic ester monomer and the aromatic vinyl monomer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resin injection molded body.

  Injection molding is the most important molding method for thermoplastic resins, and has greatly contributed to mass production and cost reduction of resin products around us. In recent years, more precise injection molding has become possible, and even moldings such as lenses and prisms that have been manufactured by cutting or casting methods and require high precision can be molded by injection molding. On the other hand, as fluid injection molding becomes possible, high fluidity is required for the resin itself as a material. This is because by increasing the fluidity of the resin itself when it melts, the resin reaches the details of the mold and enables precise transfer.

  The fluidity of the molten resin can be controlled to some extent by the resin structure, molecular weight, and molding temperature. When the resin structure is changed and the glass transition temperature is lowered, the fluidity of the molten resin is also lowered, but the heat resistance during the practical use of the molded article cannot be obtained. Although the fluidity of the molten resin can also be lowered by reducing the molecular weight, the mechanical properties are lowered. The higher the molding temperature, the lower the fluidity of the molten resin, but the generation of so-called silver, which deteriorates the mechanical properties due to thermal deterioration, is colored, or the appearance of the molded product becomes poor due to the generated volatile gas. Therefore, it is necessary to select within a limited range.

  Even in the temperature range where molding is possible, especially in optical applications, deterioration of color tone due to coloring is the most serious problem, and even slight coloring may cause significant performance degradation such as color unevenness and brightness unevenness. is necessary. Therefore, it is strongly desired to improve the thermal decomposition resistance of the resin. In addition, advanced heat decomposability is required from the point that attempts are being made to recycle scrap materials such as sprue portions and runner portions that are discharged, crushed, and reshaped.

The technology of hydrogenating aromatic rings of styrene resins (also called nuclear hydrogenation) has been known for a long time. Polyvinylcyclohexane obtained from polystyrene has the disadvantage of being inferior in mechanical strength, but it has transparency and heat distortion. It is an excellent resin. Due to its excellent transparency and heat distortion resistance, application to an optical disk substrate has been studied (see Patent Document 1). A resin obtained by nuclear hydrogenation of MS resin, which is a copolymer of methyl methacrylate and styrene, is also disclosed in some compositions as an example of application to this optical disc application (see Patent Document 2). Since the adhesiveness is insufficient and the heat distortion resistance is not always sufficient, the performance of the optical disk substrate may not be sufficiently exhibited. An example applied to a plastic lens is also disclosed with some compositions (see Patent Document 3).
Japanese Patent Laid-Open No. 63-43910 JP-A-6-25326 JP-A-4-75001

  An object of the present invention is to provide an injection molded article using the above-described resin excellent in fluidity and heat decomposability at the time of melting.

The present invention has been intensively studied in view of the above circumstances, and as a result, the fragrance of a copolymer comprising a composition of a specific structural unit obtained by polymerizing a monomer composition selected from a (meth) acrylic acid ester monomer and an aromatic vinyl monomer. It has been found that by injection molding a resin obtained by hydrogenating a ring, an injection molded product in which a fine pattern is precisely transferred can be obtained with good yield, and the present invention has been achieved. That is, the present invention relates to a structural unit (B mole) derived from an aromatic vinyl monomer in a structural unit of a copolymer obtained by polymerizing a monomer composition containing a (meth) acrylic acid ester monomer and an aromatic vinyl monomer. A resin obtained by hydrogenating an aromatic ring of a copolymer having a molar ratio (A / B) of a structural unit (A mole) derived from a (meth) acrylate monomer of 0.25 to 4.0 is used. The present invention relates to an injection molded body. In the present invention, (meth) acrylic acid is a notation indicating methacrylic acid and acrylic acid.

  Since the injection-molded article obtained by the present invention uses a resin having high thermal decomposition resistance and excellent fluidity at the time of melting, a fine pattern of a mold can be accurately transferred. Moreover, since the heat-resistant decomposition property of the raw material resin is excellent, even if the discharged end material is collected and reused and molded, there is little deterioration in physical properties.

  Specific examples of the (meth) acrylic acid ester monomer used in the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate, and (meth) acrylic acid. (Meth) acrylic acid alkyls such as stearyl, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate; (meth) acrylic acid (2-hydroxyethyl), (meth) acrylic acid (2-hydroxypropyl), ( (Meth) acrylic acid (2-hydroxy-2-methylpropyl) and other (meth) acrylic acid hydroxyalkyls; (meth) acrylic acid (2-methoxyethyl), (meth) acrylic acid (2-ethoxyethyl) and the like Alkoxyalkyl (meth) acrylates; benzyl (meth) acrylate and (meth) acrylic acid (Meth) acrylic acid esters having an aromatic ring such as nyl; and (meth) acrylic acid esters having a phospholipid-like functional group such as 2- (meth) acryloyloxyethyl phosphorylcholine, etc. From the viewpoint of physical properties, it is preferable to use alkyl methacrylate alone or to use alkyl methacrylate and alkyl acrylate together. Furthermore, it is preferable to use methyl methacrylate 80-100 mol% and alkyl acrylate 0-20 mol%. Of the alkyl acrylates used, particularly preferred are methyl acrylate or ethyl acrylate.

  Specific examples of the aromatic vinyl monomer used in the present invention include aromatic vinyl compounds such as styrene, α-methylstyrene, p-hydroxystyrene, alkoxystyrene, and chlorostyrene, and styrene is preferably used.

  A known method can be used as a method for polymerizing these monomers, but a method based on radical polymerization may be simple industrially. For the radical polymerization, a known method such as a bulk polymerization method, a solution polymerization method, an emulsion polymerization method or a suspension polymerization method can be appropriately selected. For example, as an example of a bulk polymerization method or a solution polymerization method, a continuous polymerization method in which a monomer composition containing a monomer, a chain transfer agent, and a polymerization initiator is continuously fed to a complete mixing tank and polymerized at 100 to 180 ° C. and so on. In solution polymerization methods, hydrocarbon solvents such as toluene, xylene, cyclohexane and methylcyclohexane, ester solvents such as ethyl acetate, ketone solvents such as acetone and methyl ethyl ketone, ether solvents such as tetrahydrofuran and dioxane, methanol and isopropanol, etc. A solvent, such as an alcohol solvent, is fed with the monomer composition. The reaction liquid after the polymerization can be extracted from the polymerization tank and introduced into a devolatilizing extruder or a vacuum devolatilization tank to devolatilize the volatile matter and obtain a resin.

  In the case of a vinyl polymer such as a copolymer of methacrylic acid esters (also referred to as a methacrylic resin), the composition of the constituent unit of the copolymer is not necessarily the same as the composition of the charged monomer, and is actually determined by the polymerization reaction. Determined by the amount of monomer incorporated into the polymer. The ratio of the constituent units of the copolymer is the same as the charged monomer composition ratio when the polymerization rate is 100%, but in practice, it is often produced at a polymerization rate of 50 to 80%. Since it is easily incorporated into the polymer, there is a difference between the charged composition of the monomer and the composition of the constituent unit of the copolymer, so the composition ratio of the charged monomer needs to be adjusted appropriately. The molar ratio (A / B) of the structural unit (A mole) derived from the (meth) acrylic acid ester monomer to the structural unit (B mole) derived from the aromatic vinyl monomer used in the hydrogenation reaction in the present invention is 0. 25 or more and 4.0 or less. If it is less than 0.25, the mechanical strength may be inferior and the practicality may not endure. When it exceeds 4.0, since there are few aromatic rings hydrogenated, performance improvement effects, such as a glass transition temperature improvement by hydrogenation reaction, may be insufficient. If a more preferable range is illustrated from the standpoint of balance of physical properties, 1.0 to 4.0. Hereinafter, a particularly preferable range is 1.0 or more and 2.5 or less.

  The copolymer obtained by the above method or the like is dissolved in an appropriate solvent and subjected to a hydrogenation reaction. The same solvent as that used in the polymerization may be used, or a different solvent may be used. The solvent used in the hydrogenation reaction is preferably a solvent that does not have a hydrogenated site among those having good copolymer solubility and hydrogen solubility before and after the hydrogenation reaction. For example, hydrocarbon solvents such as cyclohexane and methylcyclohexane, ester solvents such as ethyl acetate, ketone solvents such as acetone and methyl ethyl ketone, ether solvents such as tetrahydrofuran and dioxane, and alcohol solvents such as methanol and isopropanol are used. .

  For the hydrogenation reaction, a known method such as a batch reaction or a continuous flow reaction can be used in the presence of a catalyst. Preferred conditions include a hydrogen pressure of 3 to 30 MPa and a reaction temperature of 60 to 250 ° C. Done in If the reaction temperature is too low, the reaction is difficult to proceed. If the reaction temperature is too high, the molecular weight is reduced due to the cleavage of the molecular chain, and the hydrogenation reaction at the ester site is likely to proceed. In order to prevent molecular weight drop due to molecular chain scission and allow the reaction to proceed smoothly, the hydrogenation reaction is performed at an appropriate temperature and hydrogen pressure appropriately determined by the type and concentration of the catalyst used, the solution concentration of the copolymer, the molecular weight, etc. It is preferable to carry out.

  A known catalyst can be used as the catalyst. Specifically, metals such as nickel, palladium, platinum, cobalt, ruthenium, and rhodium, or compounds such as oxides, salts, and complexes of the metals are used as porous carriers such as carbon, alumina, silica, silica / alumina, and diatomaceous earth. Examples include a supported solid catalyst. Among these, those in which a metal such as nickel, palladium, or platinum is supported on carbon, alumina, silica, silica / alumina, or diatomaceous earth are preferably used. The supported amount is preferably 0.1 to 30 wt%.

  The hydrogenation reaction rate is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more with respect to the aromatic ring. If it is less than 70%, the resin may become cloudy and the transparency may decrease, which is not preferable.

  In the present invention, various injection moldings such as injection compression molding, ultra-high speed injection molding, co-injection molding, and gas assist injection molding are possible. A known mold structure can also be used. The temperature conditions at the time of injection molding can be set widely, but usually a range of 200 ° C. or more and less than 300 ° C. is preferable. If it is less than 200 ° C., the plasticization is not sufficiently performed, and there is a possibility that the mold pattern cannot be accurately transferred, which is not preferable. On the other hand, if it exceeds 300 ° C., random decomposition of the main chain proceeds to generate a volatile component, and the appearance of the molded article is impaired, which is not preferable. A more preferred range is 210 ° C. to 280 ° C., and a particularly preferred range is 220 ° C. to 270 ° C.

  Since the injection-molded article of the present invention is excellent in thermal decomposition resistance, it can be used by crushing end materials such as sprue parts and / or runner parts discharged during injection molding, and mixing them with the raw resin. Product yield is greatly improved. Usually, when a thermoplastic resin is repeatedly thermoformed, the thermoplastic resin deteriorates due to the heat history and becomes colored, but the injection molded article of the present invention can minimize it. Of course, it is possible to manufacture a molded body from only the end material, but in order to stabilize the quality of the product, it is preferable to use it mixed with the raw material resin. The ratio of blending the mill ends is preferably 20% by weight or less, more preferably 10% by weight or less of the sprue part and / or the runner part with respect to the total of the resin and the sprue part and / or the runner part. Especially preferably, it is 5 weight% or less.

  In obtaining the injection molded article of the present invention, a good molded article can be obtained even in a state where no antioxidant or the like is added to the resin, but the effect can be obtained by adding an appropriate antioxidant. Can be increased. Known antioxidants can be used, and specific examples include hindered phenolic antioxidants and phosphoric acid antioxidants, which may be used alone or in combination. The addition amount is preferably about 50 to 10,000 ppm with respect to the resin.

  Further, if necessary, other additives such as mold release agents, antistatic agents, colorants such as pigments and dyes, UV absorbers, plasticizers, lubricants, difficult to the extent that the balance of the injection molded article of the present invention is not impaired. You may mix | blend a flame retardant, antibacterial agent, a light-diffusion agent, etc. It is also effective to spray a mold release agent on the mold to improve the releasability, but if the amount is large, the appearance of the surface of the molded body will be damaged. It is preferable to attach.

  The injection-molded article of the present invention is an article excellent in color tone with few molding defects due to thermal deterioration or the like. Specific applications include miscellaneous goods, daily necessities, electronic and electrical product parts, medical instrument parts, automobile parts, aircraft parts, etc., but various light guide plates and light guides, optical fiber connection couplers, optical waveguides, displays It is most suitable for optical articles that require precision transfer properties such as front panels, plastic lenses, prisms, plastic lens substrates, optical filters, optical films, and optical recording medium substrates.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by these examples. In addition, the evaluation method of injection molding and resin used as the raw material is as follows.

(1) The molar ratio of structural units in the copolymer was calculated by ¹ H-NMR measurement (400 MHz).
(2) The hydrogenation reaction rate of the resin was evaluated by the rate of decrease in absorption at 260 nm in the UV spectrum measurement before and after the hydrogenation reaction.
(3) The glass transition temperature (Tg) of the resin was evaluated by using a DSC220 type differential scanning calorimetry (DSC) apparatus manufactured by Seiko Denshi Kogyo Co., Ltd. 10 mg of resin was added at 10 ° C./min. And calculated by the midpoint method.
(4) The transferability of the molded product was evaluated by preparing 20 molded products after various measurement conditions and holding pressure conditions were changed and stable molded products were obtained. In the case where the wrinkle pattern is formed in every corner, the mark is given as “◯”, when the wrinkle pattern has transfer unevenness even at one place, “△”, and when the transfer unevenness is observed in all the molded articles, “x” is given.
(5) The appearance of the molded product was evaluated by producing and evaluating 20 molded products after various measurement conditions and holding pressure conditions were changed and stable molded products were obtained. The case where there was no silver was marked as ◯, and the case where silver was generated was marked as △. The case where silver was recognized in all of the molded bodies was rated as x.
(6) The recyclability of the molded body is that the sprue part and / or runner part discharged during the injection molding is crushed, a predetermined amount is mixed with the raw material resin, the recycled molded body is molded, and the original molding is performed. The YI values of the two molded bodies, the molded body and the recycled molded body, were measured, and the difference was evaluated as the recyclability. The YI value was measured by a transmission method using a 3.2 mm thick disc using a chromaticity / turbidity measuring device COH-300A manufactured by Nippon Denshoku Industries Co., Ltd. In general, the resin is colored yellow by receiving a thermal history. Therefore, it can be said that the smaller the value, the better the recyclability.

[Production of resin]
<Production Example 1>
Methyl methacrylate 59.9 mol% and styrene 39.9 mol% as monomer components, n-dodecyl mercaptan 0.17 mol% as chain transfer agent, and t-amylperoxy 2-ethylhexanoate as polymerization initiator the 4.2 × 10 ^-3 mol% of the monomer composition was blended so that the concentration was continuously fed at 1 kg / time 10 l complete mixing tank with a helical ribbon blade, the average residence time of 2.5 hours, Continuous polymerization was performed at a polymerization temperature of 150 ° C.

  The reaction liquid is withdrawn from the bottom with a gear pump so that the polymerization tank liquid level is constant, and while maintaining the polymerization liquid at 150 ° C., it is introduced into a devolatilizing extruder equipped with a vent port to devolatilize the volatile matter, The strand was cut into pellets (resin A1). At this time, the molar ratio (A / B) of the constituent monomer units in the copolymer was 1.5.

  The resin A1 was dissolved in dioxane to prepare a 10 wt% dioxane solution. A 1000 mL autoclave was charged with 500 parts by weight of a 10 wt% dioxane solution and 1 part by weight of 10 wt% Pd / C (manufactured by NE Chemcat), and the hydrogenation reaction was carried out by maintaining the hydrogen pressure at 10 MPa at 200 ° C. for 15 hours. After removing the catalyst with a filter, dioxane was heated to distill off, the reaction solution was concentrated to 50 wt%, and diluted with toluene again to 10 wt% to replace the solvent, thereby obtaining a 50 wt% toluene solution. This was again introduced into a devolatilizing extruder equipped with a vent port, volatile components were devolatilized, and the strands were cut to obtain pellets (resin A2). The hydrogenation reaction rate was 96%. The glass transition temperatures of the resins A1 and A2 were evaluated. The results are shown in Table 1.

<Production Example 2>
A resin was synthesized in the same manner as in Production Example 1 except that 80.0 mol% methyl methacrylate and 19.8 mol% styrene were used as monomer components (resin B1). The molar ratio (A / B) of the constituent monomer units in the copolymer was 4.0.

  Pellets were obtained by a hydrogenation reaction in the same manner as in Production Example 1 except that resin B1 was used instead of resin A1 (resin B2). The hydrogenation reaction rate was 100%. The glass transition temperatures of Resin B1 and Resin B2 were evaluated. The results are shown in Table 1.

<Production Example 3>
A resin was synthesized in the same manner as in Production Example 1 except that 20.4 mol% methyl methacrylate and 79.4 mol% styrene were used as monomer components (resin C1). The molar ratio (A / B) of the constituent monomer units in the copolymer was 0.25.

  Pellets were obtained by a hydrogenation reaction in the same manner as in Production Example 1 except that resin C1 was used instead of resin A1 (resin C2). The hydrogenation reaction rate was 94%. The glass transition temperatures of Resin C1 and Resin C2 were evaluated. The results are shown in Table 1.

[Production of molded body]
<Example 1>
By using an electric injection molding machine (FANUC AUTOSHOT-100B) using resin A2, the cylinder temperature is set to 260 ° C., the mold temperature is set to (glass transition temperature-30) ° C., the cooling time is 40 seconds, and the thickness is 50 mm × 50 mm. A 3.2 mm flat plate test piece (with a wrinkle pattern on one side of the mold) was prepared, and the transferability and appearance (whether silver was generated) of the molded body were visually evaluated. The results are shown in Table 1.

<Example 2>
A test piece was prepared in the same manner as in Example 1 except that the resin B2 was used instead of the resin A2, and the transferability and appearance (whether silver was generated) of the molded body were visually evaluated. The results are shown in Table 1.

<Example 3>
A test piece was prepared in the same manner as in Example 1 except that the resin C2 was used instead of the resin A2, and the transferability and appearance (whether silver was generated) of the molded body were visually evaluated. The results are shown in Table 1.

<Comparative Example 1>
A test piece was prepared in the same manner as in Example 1 except that the resin A1 was used instead of the resin A2, and the transferability and appearance (whether silver was generated) of the molded body were visually evaluated. The results are shown in Table 1.

<Comparative example 2>
A test piece was prepared in the same manner as in Example 1 except that the resin B1 was used instead of the resin A2, and the transferability and appearance (whether silver was generated) of the molded body were visually evaluated. The results are shown in Table 1.

<Comparative Example 3>
A test piece was prepared in the same manner as in Example 1 except that the resin C1 was used instead of the resin A2, and the transferability and appearance (whether silver was generated) of the molded body were visually evaluated. The results are shown in Table 1.

[Evaluation of recyclability]
<Example 4>
In the same manner as in Example 1, a disk having a diameter of 50φ and a thickness of 3.2 mm was formed using the resin A2. After sprue part and runner part discharged at the time of injection molding of the molded product are crushed into flakes, resin A2 and 10% by weight of sprue part and runner part with respect to the total of sprue part and runner part are mixed (dry blend) Then, a 3.2 mm thick disk (recycled molded body) was formed. Recyclability and the appearance of the recycled molded body were evaluated. The results are shown in Table 2.

<Example 5>
A disk was prepared in the same manner as in Example 4 except that the resin B2 was used instead of the resin A2, and the recyclability and the appearance of the recycled molded body (whether silver was generated) were evaluated. The results are shown in Table 2.

<Example 6>
A disk was prepared in the same manner as in Example 4 except that the resin C2 was used instead of the resin A2, and the recyclability and the appearance of the recycled molded body (whether silver was generated) were evaluated. The results are shown in Table 2.

<Comparative example 4>
A disk was prepared in the same manner as in Example 4 except that the resin A1 was used instead of the resin A2, and the recyclability and the appearance of the recycled molded body (whether silver was generated) were evaluated. The results are shown in Table 2.

<Comparative Example 5>
A disk was prepared in the same manner as in Example 4 except that the resin B1 was used instead of the resin A2, and the recyclability and the appearance of the recycled molded body (whether silver was generated) were evaluated. The results are shown in Table 2.

<Comparative Example 6>
A disk was prepared in the same manner as in Example 4 except that the resin C1 was used instead of the resin A2, and the recyclability and the appearance of the recycled molded body (whether silver was generated) were evaluated. The results are shown in Table 2.

Claims (5)

(Meth) acrylic acid ester with respect to structural unit (B mole) derived from aromatic vinyl monomer in the structural unit of copolymer obtained by polymerizing monomer composition containing (meth) acrylic acid ester monomer and aromatic vinyl monomer An injection-molded article using a resin obtained by hydrogenating an aromatic ring of a copolymer having a monomer-derived structural unit (A mole) molar ratio (A / B) of 0.25 to 4.0. The copolymer whose molar ratio (A / B) of the structural unit (A mol) derived from the (meth) acrylic acid ester monomer to the structural unit (B mole) derived from the aromatic vinyl monomer is 1.0 to 4.0 The injection-molded article according to claim 1, wherein a resin obtained by hydrogenating the aromatic ring is used. Resin obtained by hydrogenating an aromatic ring of a copolymer in which the (meth) acrylic acid ester monomer is composed of 80 to 100 mol% of methyl methacrylate and 0 to 20 mol% of alkyl acrylate, and the aromatic vinyl monomer is styrene. The injection-molded article according to claim 1 or 2, comprising: The injection-molded article according to any one of claims 1 to 3, wherein a resin having a hydrogenation reaction rate of 70% or more with respect to the aromatic ring is used. The sprue part and / or the runner part discharged at the time of injection molding are crushed, and the sprue part and / or the runner part are mixed and used in an amount of 20% by weight or less based on the total of the resin and the sprue part and / or the runner part. The injection-molded article according to any one of claims 1 to 4.