JP2007254733A - Process for producing hydrogenated polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a highly transparent hydrogenated polymer including a step of hydrogenating aromatic rings of an aromatic vinyl compound-(meth) acrylate copolymer, the hydrogenated polymer is stably and rapidly produced for a long period of time or repeatedly. <P>SOLUTION: The invention relates to the process for producing the hydrogenated polymer comprising hydrogenation of the copolymer having a ratio, A/B from 0.25 to 4.0 (A is a molar number of constitutional units derived from the (meth)acrylate monomer, and B is a molar number of constitutional units derived from the aromatic vinyl monomer) in a solvent in the presence of a catalyst which is composed of zirconium oxide supporting palladium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a process for hydrogenating an aromatic ring in the presence of a copolymer of an aromatic vinyl compound and (meth) acrylate in the presence of a support mainly composed of zirconium oxide and a palladium supported on the support. The present invention relates to a method for producing a hydrogenated polymer containing The hydrogenated polymer obtained by this method exhibits high transparency, low birefringence, high heat resistance, high surface hardness, low water absorption, low specific gravity, high transferability, and excellent releasability. In particular, since it has excellent characteristics required for optical materials, it can be used in a wide range of applications such as optical lenses, light guide plates, light diffusion plates, optical disk substrate materials, and front panels.

  In recent years, amorphous plastics such as acrylic resin, methacrylic resin, styrene resin, polycarbonate resin, and cyclic polyolefin resin have been used in various applications. There is much demand as optical materials such as. This type of optical material is required to have not only high transparency but also high performance with excellent balance of high heat resistance, low water absorption, and high mechanical properties.

  Conventionally used materials do not have all of these requirements but have respective problems to be solved. For example, polystyrene has the disadvantages that it is mechanically brittle, has a large birefringence, and has poor transparency. Polycarbonate is excellent in heat resistance, but it also has a large birefringence and transparency is almost the same as that of polystyrene. Polymethyl methacrylate has high transparency but has a very high water absorption rate. Therefore, polymethyl methacrylate has a problem of poor dimensional stability and low heat resistance. Polyvinylcyclohexane obtained by hydrogenating an aromatic ring of polystyrene is excellent in transparency, but has problems of low mechanical strength, poor heat stability, and poor adhesion to other materials (Patent Document 1, Patent) Literature 2, Patent Literature 3). As a method for improving adhesion, there is an example of mixing a hydrogenated aromatic ring of polystyrene, a polymer in which a double bond of a conjugated diene-styrene copolymer and an aromatic ring are hydrogenated, and a saturated hydrocarbon resin (Patent Literature). 4) The operation is complicated. In addition, after copolymerizing a vinyl aromatic compound such as styrene and an unsaturated dibasic acid such as maleic anhydride, hydrogenation of 30% or more of the aromatic ring improves transparency and birefringence compared to polystyrene. However, it cannot be denied that the optical properties are inferior to those of acrylic resins.

  Further, a copolymer of methyl methacrylate (hereinafter referred to as MMA) and styrene (hereinafter referred to as MS resin) has high transparency and excellent balance of dimensional stability, rigidity, specific gravity and the like. Although it is a resin, there is a problem that the birefringence is large. Resins obtained by hydrogenating the aromatic ring of the MS resin (hereinafter referred to as MSH), in particular, MSH having a MMA copolymerization rate of 50% or more has a significantly improved birefringence compared with the MS resin, transparency, Excellent balance between heat resistance and mechanical properties.

  Hydrogenation of an aromatic ring of an aromatic polymer is already known (Patent Document 6). However, in order to increase transparency, it is necessary to increase the hydrogenation rate of the aromatic ring, and the hydrogenation rate of the aromatic ring is approximately 100. If it is not%, it has been said that a highly transparent resin cannot be obtained. This is because, when the hydrogenation rate of the aromatic ring is low, a block body is formed and the total light transmittance is lowered.

  In order to facilitate separation from the reaction substrate, it is preferable to use a solid catalyst, and a metal such as Pd, Pt, Rh, Ru, Re, Ni is supported on a support such as activated carbon, alumina, silica, diatomaceous earth. A solid catalyst is mainly used. Many examples relating to hydrogenation of polymers such as conjugated diene polymers as well as aromatic polymers are known, but they are difficult to react due to their high molecular weight, and it is difficult to obtain a high hydrogenation rate and high reaction rate. It is also known that the activity tends to decrease when the catalyst is used repeatedly. When the catalytic activity decreases, the hydrogenation rate decreases and the transparency of the resin is impaired. In order to improve the catalytic activity, the type of support, pore structure and particle size have been studied. For example, hydrogenated polystyrene having a hydrogenation rate of an aromatic ring of about 70% using a catalyst in which palladium is supported on a silica support having a particle size of less than 100 μm (Patent Document 2), or having a pore size of 600 mm. There is an example in which hydrogenated polystyrene is obtained using a catalyst in which Pt and Rh are supported on a silica support having a large pore exceeding (Patent Document 7). Similarly, using a catalyst in which a group VIII metal is supported on a porous support whose pore volume is 95% or more and having a pore diameter of 450 mm, and the metal surface area is within 75% of the support surface area, the hydrogenation rate of the aromatic ring is increased. There is also an example in which the ethylenically unsaturated bond is hydrogenated at a high hydrogenation rate (Patent Document 8).

  When a catalyst in which a group VIII metal is supported on silica or alumina having a pore volume of 100 to 1000 mm and having a pore volume of 70 to 25% of the total pore volume is used, the aromatic ring of polystyrene is completely hydrogenated without lowering the molecular weight ( Patent Document 9), a commercially available ordinary compound for low molecular weight compounds obtained by supporting a metal of group VIII on a silica or alumina support having a pore size of 100 to 1000 mm and a pore volume of less than 15% of the total pore volume. It has been disclosed that when a hydrogenation catalyst is used in the presence of an ether group-containing hydrocarbon, the aromatic ring of polystyrene can be completely hydrogenated without decreasing the molecular weight (Patent Document 10). It is disclosed that a catalyst in which a metal is supported on an oxide of a group IVa element such as titanium oxide or zirconium oxide exhibits high activity even when reused in a hydrogenation reaction of a conjugated diene polymer such as NBR (Patent Document). 11). However, it only describes the hydrogenation reaction of conjugated diene polymers, and there is no mention of hydrogenation of aromatic rings. After adding an alkali metal or an alkaline earth metal on a carrier having a pore diameter of 100 to 100,000 nm and a volume of 50 to 100% of the total pore volume, 90% or more of the platinum group metal has a surface layer portion (of the carrier diameter). If the catalyst supported so as to exist within 1/10) is used, the unsaturated bond (including aromatic ring) of the aromatic-conjugated diene copolymer can be efficiently hydrogenated and the elution of metal components can be suppressed. (Patent Document 12).

  Further, catalytic activity is improved by removing the catalyst poison from the polymerization reaction solution with activated alumina and then hydrogenating (Patent Document 13), and the reaction linear velocity in the fixed bed is improved to increase productivity. (Patent Document 14) has been reported.

  Since it is a polymer reaction, the solvent contributes greatly to the hydrogenation reaction of the aromatic ring. So far, many reaction solvents such as hydrocarbons, alcohols, ethers and esters have been generally used (Patent Document 15). Hydrocarbons and alcohols have low solubility in resins. Ethers such as 1,4-dioxane have a low ignition point and must be replaced with other solvents such as toluene when performing high temperature devolatilization extrusion. Tetrahydrofuran is susceptible to ring-opening reactions. There is a problem of stability. Esters are safe and relatively stable, and the reaction proceeds rapidly. However, depending on the hydrogenation rate, there is a problem that the reaction solution and the solid resin become cloudy and the transparency is lowered. Therefore, a method for obtaining a hydrogenated aromatic polymer having a high degree of transparency in a safe, stable and rapid manner by adding an alcohol to the ester is disclosed. However, two kinds of solvents are used in combination, and the separation operation becomes complicated. Moreover, although a method for achieving high transparency even at a low hydrogenation rate by adding alcohol or water to an ether solvent is disclosed (Patent Document 16), since applicable aromatic polymers are limited, Often not applicable.

As described above, there are many difficult problems in obtaining an aromatic ring hydrogenated aromatic polymer having high optical properties. In particular, polymers obtained by hydrogenating the aromatic ring of a copolymer of an aromatic vinyl compound and (meth) acrylate are excellent in high transparency, low birefringence, high heat resistance, high surface hardness, low water absorption, low specific gravity, etc. However, a useful method for obtaining such a hydrogenated polymer for a long period of time or repeatedly stably and rapidly has not been obtained so far.
JP 2003-138078 A Japanese Patent No. 3094555 JP 2004-149549 A Japanese Patent No. 2725402 Japanese Patent Publication No. 7-94496 German Patent Application No. 1131885 Japanese National Patent Publication No. 11-504959 Japanese Patent No. 3200057 JP 2002-521509 A Special table 2002-521508 gazette JP-A-1-213306 JP 2000-95815 A Special table 2003-529646 gazette JP 2002-249515 A JP-T-2001-527095 Japanese Patent No. 2890748

  The present invention provides a method for producing a highly transparent aromatic ring hydrogenated polymer from an aromatic vinyl compound- (meth) acrylate copolymer quickly and stably over a long period of time or repeatedly.

  As a result of intensive studies, the inventors have determined that the molar ratio (A / B) of the structural unit (A mole) derived from the (meth) acrylate monomer to the structural unit (B mole) derived from the aromatic vinyl monomer is within a specific range. When the aromatic vinyl compound- (meth) acrylate copolymer is hydrogenated in the presence of a catalyst in which palladium is supported on zirconium oxide, a highly transparent aromatic ring hydrogenated polymer can be obtained stably and rapidly. The headline, the present invention has been reached.

That is, the present invention provides an aromatic having A / B (A is the number of moles of a structural unit derived from a (meth) acrylate monomer and B is the number of moles of a structural unit derived from an aromatic vinyl monomer) is 0.25 to 4.0. The present invention relates to a method for producing a hydrogenated polymer comprising a step of hydrogenating an aromatic ring in a vinyl compound- (meth) acrylate copolymer in a solvent in the presence of a catalyst in which palladium is supported on zirconium oxide.
The present invention further relates to a hydrogenated polymer obtained by the production method.
The invention further relates to an optical composition comprising the hydrogenated polymer.

  According to the production method of the present invention, the aromatic ring of a copolymer of an aromatic vinyl compound and (meth) acrylate can be stably hydrogenated for a long period of time, and the hydrogenated aromatic vinyl obtained thereby The copolymer polymer of the compound and (meth) acrylate exhibits high transparency, low birefringence, high heat resistance, high surface hardness, low water absorption, low specific gravity, high transferability, and excellent releasability. In particular, it has excellent characteristics as an optical material, and can be used for a wide range of applications such as optical lenses, light guide plates, light diffusion plates, optical disk substrate materials, front panels and the like.

  Hereinafter, the present invention will be described in detail. Specific examples of the aromatic vinyl compound used in the present invention include aromatic vinyl compounds such as styrene, α-methylstyrene, p-hydroxystyrene, alkoxystyrene, and chlorostyrene, with styrene being preferred.

The (meth) acrylate used in the present invention specifically includes methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, (Meth) acrylic acid cyclohexyl, (meth) acrylic acid alkyl such as isobornyl alkyl; (meth) acrylic acid (2-hydroxymethyl), (meth) acrylic acid (2-hydroxypropyl), (meth) acrylic Hydroxyalkyl (meth) acrylates such as acid (2-hydroxy-2-methylpropyl); (meth) acrylic such as (meth) acrylic acid (2-methoxyethyl), (meth) acrylic acid (2-ethoxyethyl) Acid alkoxyalkyl; aromatic rings such as benzyl (meth) acrylate and phenyl (meth) acrylate (Meth) acrylic acid ester having a phospholipid-like functional group such as 2- (meth) acryloyloxyethyl phosphorylcholine and the like, and methacrylic acid from the balance of physical properties. It is preferable to use alkyl alone or to use alkyl methacrylate and alkyl acrylate together. When using together, it is preferable to use 80-100 mol% of alkyl methacrylate and 0-20 mol% of alkyl acrylate. As the alkyl methacrylate, methyl methacrylate is particularly preferable, and as the alkyl acrylate, methyl acrylate or ethyl acrylate is particularly preferable.
In this specification, “acrylic acid” and “methacrylic acid” are collectively referred to as (meth) acrylic acid, and “acrylate” and “methacrylate” are collectively referred to as (meth) acrylate.

  Polymerization of the aromatic vinyl compound and (meth) acrylate can be carried out by a known method, but industrially, a method by radical polymerization may be simple. 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, in the bulk polymerization method and the solution polymerization method, continuous polymerization is performed at 100 to 180 ° C. while continuously feeding a monomer composition containing a monomer, a chain transfer agent, and a polymerization initiator to a complete mixing tank. In the solution polymerization method, 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. An alcohol solvent or the like is fed together with the monomer composition. The reaction liquid after the polymerization can be taken out from the polymerization tank and introduced into a devolatilization extruder or a vacuum devolatilization tank to remove the volatile matter to obtain a copolymer.

  The constitutional unit composition of the aromatic vinyl compound- (meth) acrylate copolymer used in the present invention does not necessarily match the composition of the charged monomer, and the amount of each monomer actually incorporated into the copolymer by the polymerization reaction. Varies depending on the polymerization rate and the reactivity of the monomer. The constitutional unit composition of the copolymer is the same as the charged monomer composition 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 coalescence, a deviation occurs between the charged composition of the monomer and the compositional unit of the copolymer. Therefore, it is necessary to appropriately adjust the charged monomer composition.

  In the aromatic vinyl compound- (meth) acrylate copolymer, the molar ratio (A / B) of the structural unit (A mole) derived from the (meth) acrylate monomer to the structural unit (B mole) derived from the aromatic vinyl compound monomer is It is 0.25 to 4.0, preferably 0.4 to 4.0. If it is less than 0.25, the mechanical strength is inferior and may not be practical. When 4.0 is exceeded, since there are few aromatic rings hydrogenated, performance improvement effects, such as a raise of the glass transition temperature by hydrogenation, may be insufficient.

  The weight average molecular weight of the aromatic vinyl compound- (meth) acrylate copolymer is preferably 10,000 to 1,000,000, more preferably 50,000 to 700,000, and even more preferably 100,000 to 500,000. preferable. Copolymers of less than 10,000 or more than 1,000,000 can also be hydrogenated by the method of the present invention, but less than 10,000 may not be practical in terms of mechanical strength and the like. If it exceeds 1,000,000, handling may be difficult in terms of viscosity and the like. The weight average molecular weight was obtained by gel permeation chromatography (GPC) using THF as a solvent and calibrating with standard polystyrene.

  Since the hydrogenated polymer obtained by the method of the present invention transmits light in the visible light region satisfactorily, its appearance is transparent. It is preferable that the total light transmittance of a molded product having a thickness of 3.2 mm measured by a method defined in JIS K7105 is 90% or more. Since the loss due to reflection on the surface of the molded product is inevitable, the upper limit of the total light transmittance depends on the refractive index. When used as an optical material, a higher degree of transparency may be required, so that the total light transmittance is more preferably 91% or more, and further preferably 92% or more. In order to obtain such transparency, it is preferable that the aromatic ring in the starting copolymer is homogeneously hydrogenated.

  In general, in the hydrogenation of the aromatic ring of the aromatic vinyl copolymer, it is difficult to completely hydrogenate all aromatic rings, and usually an unhydrogenated aromatic ring remains. This unhydrogenated aromatic ring often causes cloudiness. One of the causes is that a site containing a hydrogenated aromatic ring and a site containing an unhydrogenated aromatic ring each form a block. In particular, when the hydrogenation rate of the aromatic ring is low, a block is easily formed. In order to suppress block formation in the method of the present invention, the hydrogenation rate of the aromatic ring is preferably 70% (mol%) or more, more preferably 85% (mol%) or more. Generally, the molecular weight of the aromatic vinyl copolymer is distributed, the aromatic ring of the low molecular weight aromatic vinyl copolymer is preferentially hydrogenated, and the aromatic ring of the high molecular weight aromatic vinyl copolymer is hydrogenated. It can cause cloudiness to remain. That is, if the hydrogenation rate of the aromatic ring of the high molecular weight aromatic vinyl copolymer is significantly lower than that of the low molecular weight aromatic vinyl copolymer, the aromatic ring of the low molecular weight aromatic vinyl copolymer is preferentially Hydrogenated, the resulting polymer tends to become cloudy. However, if the hydrogenation rate of the aromatic ring of the high molecular weight aromatic vinyl copolymer is improved to reduce the unhydrogenated aromatic ring and the compatibility of the whole polymer is increased, the domain disappears and high transparency is exhibited. It has been known. In general, a solvent or a catalyst greatly affects the prevention of white turbidity due to the difference in hydrogenation rate of the aromatic ring due to the molecular weight.

  As the catalyst used in the hydrogenation reaction in the present invention, a catalyst that increases the hydrogenation rate, does not decrease the molecular weight of the raw material copolymer, and does not induce the reaction of the solvent itself under the hydrogenation conditions is selected. . Specifically, since a high metal surface area can be obtained by supporting it, a solid catalyst in which palladium (Pd) is supported on a carrier is suitable.

In general, activated carbon, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), silica-alumina (SiO ₂ -Al ₂ O ₃ ), diatomaceous earth, titanium oxide, zirconium oxide, or the like is used as the catalyst carrier. However, when a support such as activated carbon or alumina is used, the hydrogenation of the aromatic ring is difficult to proceed uniformly, and the transparency is often insufficient. It has become clear that this problem can be solved by using a zirconium oxide support. That is, when hydrogenation is carried out in the presence of a catalyst in which palladium is supported on a zirconium oxide support, the hydrogenation rate of the aromatic ring is high, and the hydrogenation proceeds homogeneously to obtain a hydrogenated polymer having high transparency. Was found. Further, it was found that the difference in the hydrogenation rate of the aromatic ring due to the difference in the molecular weight of the aromatic vinyl compound- (meth) acrylate copolymer was small, and the hydrogenation proceeded more uniformly than expected.

  Even if the hydrogenation does not proceed homogeneously during the reaction, when the hydrogenation rate finally reaches almost 100%, the domain disappears and a highly transparent hydrogenated polymer can be obtained. However, when the catalyst is used for a long time and repeatedly, it is impossible to achieve a hydrogenation rate of almost 100%. Since hydrogenation proceeds homogeneously when hydrogenated in the presence of a catalyst in which palladium is supported on zirconium oxide, the total light transmittance is 90% or higher even when the hydrogenation rate is less than 90 mol%, for example. A hydrogenated polymer can be obtained reliably, which is extremely advantageous for industrial production.

  The homogeneity of the hydrogenation progress can be evaluated by measuring the molecular weight distribution of the polymer containing unhydrogenated aromatic rings in the product. That is, by measuring and comparing the weight average molecular weight (Mw2) of the polymer containing an unhydrogenated aromatic ring and the weight average molecular weight (Mw1) of the copolymer before hydrogenation using gel permeation chromatography. Can be evaluated. If the aromatic ring of the low molecular weight aromatic vinyl copolymer is preferentially hydrogenated, the molecular weight distribution of the polymer containing the unhydrogenated aromatic ring is greatly shifted to the high molecular weight side from the molecular weight distribution before hydrogenation. That is, the weight average molecular weight of the polymer containing an unhydrogenated aromatic ring is increased, and Mw2 / Mw1 is significantly increased. On the other hand, when the low molecular weight aromatic vinyl copolymer and the high molecular weight aromatic vinyl copolymer are almost uniformly aromatic ring hydrogenated, the molecular weight distribution of the polymer containing unhydrogenated aromatic rings is the molecular weight distribution before hydrogenation. Mw2 / Mw1 is small because the degree of shift to almost the same or higher molecular weight is small. When a catalyst in which palladium is supported on zirconium oxide is used, Mw2 / Mw1 is 1.5 or less, indicating that the hydrogenation proceeds homogeneously. When Mw2 / Mw1 is 2 or more, it indicates that the aromatic ring of the low molecular weight aromatic vinyl copolymer has been preferentially hydrogenated, and the resin may become cloudy.

  In addition, the catalyst in which palladium is supported on zirconium oxide has a very low decrease in activity even when it is reused, and hydrogenation proceeds homogeneously in the same manner as in the initial use. It is possible to obtain a polymer having

  The supported amount of palladium metal is preferably 0.01 to 50% by weight, more preferably 0.05 to 20% by weight, and still more preferably 0.1 to 10% by weight with respect to the zirconium oxide support. Although it is economically preferable that the amount of palladium, which is an expensive precious metal, be used as little as possible, when used as a zirconium oxide support, palladium can be supported in a highly dispersed state, and the hydrogenation rate per unit weight of palladium can be increased. Since it can be made very large, even when the supported amount of palladium is about 0.1 to 0.5% by weight, a sufficient hydrogenation rate can be obtained. The degree of dispersion of palladium can be measured by a known method such as a carbon monoxide pulse adsorption method. The higher the degree of dispersion, the better.

  As the precursor of palladium, known salts or complexes such as palladium chloride, palladium nitrate, and palladium acetate can be used. For the preparation of the catalyst, an aqueous solution of hydrochloric acid or sodium chloride in palladium chloride, an aqueous solution or aqueous solution of palladium nitrate, an aqueous hydrochloric acid solution in palladium acetate or an organic solvent solution can be used. A catalyst in which palladium is highly dispersed can be obtained by impregnating a zirconium oxide support with an organic solvent solution such as 1,4-dioxane, drying and removing the solvent, and calcining (preferably 200 to 800 ° C.).

The zirconium oxide support can be obtained by a general method. For example, a method of hydrolyzing zirconium oxychloride, zirconyl nitrate, zirconyl sulfate, etc., or neutralizing zirconium oxychloride, zirconyl nitrate, zirconyl sulfate, etc. with ammonia or an alkali such as ammonium carbonate, sodium hydroxide, sodium carbonate, etc. Zirconium oxide can be obtained by precipitating zirconium hydroxide or amorphous zirconium oxide hydrate and firing the precipitate. It can also be obtained by thermal decomposition of zirconium oxychloride or zirconium alkoxide or gas phase oxygen decomposition of zirconium tetrachloride. By appropriately selecting the firing temperature of zirconium oxide hydrate or zirconium hydroxide, the water content, specific surface area, pore diameter and pore volume can be changed. Since a zirconium oxide with a large specific surface area can be obtained, it is preferable to fire at 300 to 800 ° C. From the viewpoint of improving the degree of dispersion of supported palladium and hydrogenation ability, the pore diameter of the zirconium oxide support is preferably 20 to 3,000 mm, and the specific surface area is preferably 10 m ² / g or more.

  If necessary, zirconium oxide may be supported on another support, and then palladium may be supported on zirconium oxide. Further, a catalyst in which palladium is supported on zirconium oxide may be mixed and molded with a binder component such as a clay compound. In this case, the content of zirconium oxide in the entire catalyst component is preferably 10% by weight or more.

  Hydrogenation of the aromatic vinyl compound- (meth) acrylate copolymer is carried out in a suitable solvent. It is preferable to select a solvent that has good solubility of the copolymer before and after the hydrogenation reaction and hydrogen solubility, does not have a hydrogenated site, and that allows hydrogenation to proceed rapidly. Further, since the solvent is removed by devolatilization after the reaction, it is preferable that the ignition point of the solvent is high. Carboxylic acid esters are suitable as solvents that satisfy all of these requirements.

As the carboxylic acid ester, the following general formula (1):
R ¹ COOR ² (1)
(Wherein R ¹ is an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms, and R ² is an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms)
The aliphatic carboxylic acid ester shown by these is suitable. Examples of R ¹ and R ² include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, a hexyl group, and a cyclohexyl group. Esters include methyl acetate, ethyl acetate, n-butyl acetate, pentyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, n-butyl propionate, methyl n-butyrate, methyl isobutyrate, Examples include n-butyric acid-n-butyl, n-methyl valerate, n-hexanoic acid methyl, etc., particularly methyl acetate, ethyl acetate, methyl propionate, methyl isobutyrate, and methyl n-butyrate are preferably used. .

  The concentration of the aromatic vinyl compound- (meth) acrylate copolymer in the solution during the hydrogenation reaction is preferably 1 to 50% by weight, more preferably 3 to 30% by weight, and even more preferably 5 to 20% by weight. is there. Within the above range, inconvenience of handling due to a decrease in reaction rate or an increase in solution viscosity can be avoided, and it is preferable from the viewpoint of productivity and economy.

The hydrogenation of the present invention can be carried out in a known reaction mode such as a suspension bed or a fixed bed, a batch system or a continuous flow system.
When the reaction is carried out in a suspended bed, the carrier particle size is preferably from 0.1 to 1,000 μm, more preferably from 1 to 500 μm, still more preferably from 5 to 200 μm. When the particle size is within the above range, catalyst separation after the hydrogenation reaction is easy, and a sufficient reaction rate can be obtained.
When hydrogenation is carried out batchwise, the amount of catalyst used is preferably 0.0005 to 10 parts by weight as palladium with respect to 100 parts by weight of the raw material copolymer. When carrying out by a continuous flow type, the raw material copolymer solution is supplied so that the raw material copolymer supply amount per unit catalyst amount, that is, the space velocity is 0.001 to ¹ h ⁻¹ .

  Hydrogenation is preferably performed at 60 to 250 ° C. and a hydrogen pressure of 3 to 30 MPa for 3 to 15 hours. When the reaction temperature is within the above range, a sufficient reaction rate can be obtained, and decomposition of the raw material copolymer and the hydrogenated copolymer can be avoided. Further, when the hydrogen pressure is within the above range, a sufficient reaction rate can be obtained.

After the hydrogenation reaction, the catalyst is separated and recovered by a known method such as filtration or centrifugation. In consideration of coloring, influence on mechanical properties, etc., the residual metal concentration in the obtained hydrogenated polymer is preferably as small as possible. The residual metal concentration is preferably 10 ppm or less, more preferably 1 ppm or less. In order to omit complicated operations such as filtration and centrifugation, hydrogenation in a fixed bed is advantageous.
After separating the catalyst, the solvent is removed from the hydrogenated polymer solution and the hydrogenated polymer is purified. For separation of hydrogenated polymers,
(1) A method in which a solvent is continuously removed from a hydrogenated polymer solution to obtain a concentrated liquid, the concentrated liquid is extruded in a molten state, and then pelletized.
(2) A method of evaporating a solvent from a hydrogenated polymer solution to obtain a lump and pelletizing the lump.
(3) A method in which a hydrogenated polymer solution is added to a poor solvent, or a hydrogenated polymer is precipitated by adding a poor solvent to the hydrogenated polymer solution, and the precipitate is pelletized.
(4) A known method such as a method of producing a lump by contacting with hot water and pelletizing the lump can be used.

  The hydrogenated polymer obtained by the method of the present invention can be made into an optical composition by a known method. Since the optical composition containing the hydrogenated polymer has thermoplasticity, a light-diffusing optical article can be precisely and economically obtained by various thermoforming methods such as extrusion molding, injection molding, and secondary processing molding of a sheet molded body. It is possible to manufacture. Specific examples of the light diffusing optical article include a light guide plate, a light guide, a display front panel, a plastic lens substrate, an optical filter, an optical film, a lighting cover, and a lighting signboard.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not particularly limited to the following examples.

The evaluation method of resin is as follows.
(1) Hydrogenation rate of aromatic ring It evaluated by the decreasing rate of the absorption of 260 nm in the UV spectrum measurement before and after hydrogenation reaction.
(2) Weight average molecular weight The weight average molecular weight (Mw1) before hydrogenation and the weight average molecular weight (Mw3) after hydrogenation were determined by gel permeation chromatography (GPC) using an RI detector. Using THF as a solvent, calibration was performed using standard polystyrene.
(3) Homogeneity of hydrogenation The weight average molecular weight Mw2 of the polymer having an unhydrogenated aromatic ring in the reaction product was measured by GPC using a UV detector (260 nm). The homogeneity of hydrogenation was evaluated by Mw2 / Mw1. When this ratio is 1.5 or less, the homogeneity of hydrogenation is good.
(4) Dispersion degree of palladium metal Measured by a CO pulse adsorption method. Calculation was made assuming CO / Pd = 1.
(5) Total light transmittance The hydrogenated polymer powder was dried under reduced pressure for 4 hours at 80 ° C., then placed in a mirror-finished mold, and 210 ° C. using a Toho Press hydraulic press. The test piece (3.2 mm × 30 mm × 30 mm flat plate) was produced by compression heating molding at 10 MPa. The total light transmittance of this test piece was measured by a transmission method according to JIS K7105, using a chromaticity / turbidity measuring device COH-300A manufactured by Nippon Denshoku Industries Co., Ltd.

Example 1
(1) Catalyst preparation 0.0527 g (0.000235 mol) of palladium acetate was dissolved in 30 g of acetone. To the obtained solution, 4.975 g of a dried zirconium oxide support (NNC 100 manufactured by Daiichi Rare Element Co., Ltd.) was added, and the solution was impregnated with stirring at 40 ° C. Acetone was distilled off under reduced pressure at 60 ° C., followed by drying at 120 ° C. for 4 hours, followed by baking at 400 ° C. for 3 hours to prepare a 0.5 wt% Pd / ZrO ₂ catalyst. The palladium metal dispersion was 85%.
(2) Hydrogenation reaction 5 g of MMA-styrene copolymer (manufactured by Nippon Steel Chemical Co., Ltd., MS600 (MMA / styrene molar ratio = 6/4)) having a weight average molecular weight (Mw1) of 170,000 is methyl isobutyrate (IBM). Dissolved in 45 g and charged into a 200 ml autoclave with 0.25 g of 0.5% Pd / ZrO ₂ . The hydrogenation reaction was carried out at a hydrogen pressure of 9 MPa and a temperature of 200 ° C. for 12 hours. After removing the catalyst by filtration, the reaction solution was dropped into excess methanol, and the precipitated polymer was recovered. The final hydrogenation rate of this polymer was 99.1%. The total light transmittance of the thermoformed product was 92%. The reaction solution was withdrawn during the reaction, and the hydrogenation rate and the weight average molecular weight (Mw2) of the copolymer containing an unhydrogenated aromatic ring were measured. The time course of hydrogenation is shown in Table 1. All reaction liquids were transparent, and hydrogenation proceeded homogeneously.
Further, when the reaction solution was extracted while filtering, elution of palladium was not observed (0.01 ppm or less).
Thereafter, the raw material liquid was replaced, and hydrogenation was performed again for 12 hours using the recovered catalyst. The hydrogenation rate was 99.1%, and the total light transmittance of the thermoformed product was 92%. In addition, the reaction liquid extracted midway was also transparent.

Comparative Example 1
(1) Catalyst 10 wt% Pd / C (NE Chemcat PE type) was used. This product had a palladium metal dispersion of 14%.
(2) Hydrogenation reaction The hydrogenation reaction was performed in the same manner as in Example 1 except that 0.2 g of 10 wt% Pd / C (PE type manufactured by NE Chemcat) was used as a catalyst. The final hydrogenation rate was 99.1%, and the total light transmittance of the thermoformed product was 92%. However, as shown in Table 2, the reaction liquid extracted after 3 hours and 6 hours was cloudy, and the total light transmittance of the polymer thermoformed product separated from these reaction liquids was less than 90%. there were.
The raw material liquid was replaced, and the hydrogenation reaction was performed again in the same manner as in Example 1, but the hydrogenation rate was reduced to 85%.

Comparative Example 2
(1) Catalyst preparation 0.1055 g (0.00047 mol) of palladium acetate was dissolved in 30 g of acetone. To this solution, 4.975 g of α-alumina was added, and the solution was impregnated with stirring at 40 ° C. Acetone was distilled off under reduced pressure at 60 ° C., followed by drying at 120 ° C. for 4 hours, followed by calcination at 400 ° C. for 3 hours to prepare a 1 wt% Pd / Al ₂ O ₃ catalyst. The degree of palladium metal dispersion was 20%.
(2) Hydrogenation reaction A hydrogenation reaction was carried out in the same manner as in Example 1 except that 0.5 g of 1 wt% Pd / Al ₂ O ₃ was used as a catalyst and the hydrogenation time was changed to 15 hours. The final nuclear hydrogenation rate was 98.8%, and the total light transmittance of the thermoformed product was 92%. However, as shown in Table 3, the reaction liquid extracted after 4 hours and after 8 hours is cloudy, and the total light transmittance of the polymer thermoformed product separated from these reaction liquids is less than 90%. there were.
The hydrogenation reaction was performed again in the same manner as in Example 1 except that the raw material liquid was replaced and the hydrogenation time was changed to 15 h, but the hydrogenation rate was reduced to 92%.

Example 2
A hydrogenation reaction was performed in the same manner as in Example 1 except that the amount of the catalyst used was changed to 0.1 g, and a polymer was recovered. The hydrogenation rate of this polymer was 96.5%, and the total light transmittance of the thermoformed product was 92%. Moreover, all the reaction liquids extracted after 4, 6 and 9 hours were transparent.

Example 3
A hydrogenation reaction was performed in the same manner as in Example 1 except that the reaction temperature was 175 ° C., and the polymer was recovered. The hydrogenation rate of this polymer was 99.0%, and the total light transmittance of the thermoformed product was 92%. Moreover, all the reaction liquids extracted after 6 hours and 9 hours were transparent.

Example 4
A hydrogenation reaction was performed in the same manner as in Example 1 except that the reaction pressure was 7 MPa, and the polymer was recovered. The hydrogenation rate of this polymer was 96.2%, and the total light transmittance of the thermoformed product was 92%. Moreover, all the reaction liquids extracted after 6 hours and 9 hours were transparent.

Example 5
(1) Catalyst preparation 0.0105 g (0.000047 mol) of palladium acetate was dissolved in 10 g of acetone. To this solution was added 4.975 g of a dried zirconium oxide support (NNC 100 manufactured by Daiichi Rare Element Co., Ltd.), and the solution was impregnated with stirring at 40 ° C. Acetone was distilled off under reduced pressure at 60 ° C., dried at 120 ° C. for 4 hours, and calcinated at 400 ° C. for 3 hours to prepare a 0.1 wt% Pd / ZrO ₂ catalyst. The palladium metal dispersion reached 90%.
(2) Hydrogenation reaction A hydrogenation reaction was carried out in the same manner as in Example 1 except that 0.5 g of the catalyst was used, and a polymer was recovered. The hydrogenation rate of this polymer was 96.6%, and the total light transmittance of the thermoformed product was 92%. Moreover, the reaction liquid extracted after 4 hours, 6 hours, and 9 hours was all transparent.

Example 6
(1) Catalyst preparation 0.0835 g (0.00047 mol) of palladium chloride and 0.055 g (0.00094 mol) of sodium chloride were dissolved in 10 g of water. To this solution was added 9.95 g of a zirconium oxide support (NNC 100 manufactured by Daiichi Rare Element Co., Ltd.), and 10 g (0.0099 mol) of 3% formalin aqueous solution and 10 g (0.0033 mol) of 1.3% NaOH aqueous solution were further added with stirring. Palladium was deposited on zirconium oxide. Subsequently, the mixture was filtered and washed repeatedly with water until the filtrate was not clouded with a 0.1N AgNO ₃ aqueous solution, and then dried at 120 ° C. to obtain a 0.5 wt% Pd / ZrO ₂ catalyst. The degree of palladium metal dispersion was 25%.
(2) Hydrogenation reaction A hydrogenation reaction was carried out in the same manner as in Example 1 except that 0.5 g of the catalyst was used, and a polymer was recovered. The hydrogenation rate of this polymer was 98.5%, and the total light transmittance of the thermoformed product was 92%. Moreover, the reaction liquid extracted after 4 hours, 6 hours, and 9 hours was all transparent.

Example 7
(1) Catalyst preparation 0.0835 g (0.00047 mol) of palladium chloride and 9.4 cc (0.00094 mol) of 0.1N HCl were dissolved in 10 g of water. To this solution was added 9.95 g of a zirconium oxide support (NNC 100 manufactured by Daiichi Rare Element Co., Ltd.), and 10 g (0.0099 mol) of 3% formalin aqueous solution and 10 g (0.0033 mol) of 1.3% NaOH aqueous solution were further added with stirring. Palladium was deposited on zirconium oxide. Subsequently, the mixture was filtered and washed repeatedly with water until the filtrate was not clouded with a 0.1N AgNO ₃ aqueous solution, and then dried at 120 ° C. to obtain a 0.5 wt% Pd / ZrO ₂ catalyst. The degree of palladium metal dispersion was 30%.
(2) Hydrogenation reaction A hydrogenation reaction was carried out in the same manner as in Example 1 except that 0.25 g of the catalyst was used, and a polymer was recovered. The hydrogenation rate of this polymer was 97.9%, and the total light transmittance of the thermoformed product was 92%. Moreover, the reaction liquid extracted after 4 hours, 6 hours, and 9 hours was all transparent.

Example 8
(1) Catalyst preparation 0.0417 g (0.000235 mol) of palladium chloride and 4.7 cc (0.00047 mol) of 0.1N HCl were dissolved in 10 g of water. To this solution was added 4.975 g of a zirconium oxide support (NNC100 manufactured by Daiichi Rare Element Co., Ltd.), and the solution was impregnated at 40 ° C. The water was distilled off while reducing the pressure at 70 ° C., followed by drying at 120 ° C. for 4 hours and baking at 400 ° C. for 3 hours. Thereafter, reduction treatment was performed at 240 ° C. while flowing a mixed gas of 10% hydrogen-90% nitrogen at a rate of 50 cc / min to prepare a 0.5 wt% Pd / ZrO ₂ catalyst. The palladium metal dispersity was 45%.
(2) Hydrogenation reaction A hydrogenation reaction was carried out in the same manner as in Example 1 except that 0.25 g of the catalyst was used, and a polymer was recovered. The hydrogenation rate of this polymer was 99.3%, and the total light transmittance of the thermoformed product was 92%. Moreover, the reaction liquid extracted after 4 hours, 6 hours, and 9 hours was all transparent.

Example 9
(1) Catalyst preparation 0.527 g (0.00235 mol) of palladium acetate was dissolved in 300 g of acetone. To this solution was added 49.75 g of a dried zirconium oxide support (NNC 100 manufactured by Daiichi Rare Element Co., Ltd.), and the solution was impregnated with stirring at 40 ° C. Acetone was distilled off under reduced pressure at 60 ° C., followed by drying at 120 ° C. for 4 hours, followed by baking at 400 ° C. for 3 hours to prepare a 0.5 wt% Pd / ZrO ₂ catalyst. To this was added 2.7 g bentonite and 45 g water as a binder, and after kneading and extrusion molding, firing was performed at 400 ° C. Thereafter, the catalyst was crushed to a diameter of 0.5 mm to 1 mm to prepare a fixed bed reaction catalyst.
(2) Hydrogenation reaction After charging 10 g of the fixed bed reaction catalyst in a 1.5 mmφ SUS316 tubular reactor, the temperature was raised to 200 ° C. while flowing hydrogen at 9 MPa and 50 cc / min. Next, a 5 wt% methyl isobutyrate solution of MMA-styrene copolymer having a weight average molecular weight of 170,000 (manufactured by Nippon Steel Chemical Co., Ltd., MS600 (MMA / styrene molar ratio = 6/4)) at 10 g / h is used as a reactor. The fixed bed flow reaction was performed while supplying to the reactor. The hydrogenation rate after 24 hours was 98.8%, and the total light transmittance of the thermoformed product was 92%. The hydrogenation rate after continuing the hydrogenation reaction for 1000 hours was 95.0%, and the total light transmittance of the thermoformed product was 92%.

  According to the production method of the present invention, the aromatic ring of the aromatic vinyl compound- (meth) acrylate copolymer can be stably and uniformly hydrogenated over a long period of time. The obtained hydrogenated polymer exhibits high transparency, low birefringence, high heat resistance, high surface hardness, low water absorption, low specific gravity, high transferability, and excellent releasability. In particular, it has excellent characteristics as an optical material, and can be used for a wide range of applications such as optical lenses, light guide plates, light diffusion plates, optical disk substrate materials, front panels, and the like, and thus the industrial significance of the present invention is great.

Claims (11)

  A / B (A is the number of moles of the structural unit derived from the (meth) acrylate monomer, and B is the number of moles of the structural unit derived from the aromatic vinyl monomer) is 0.25 to 4.0. A method for producing a hydrogenated polymer comprising a step of hydrogenating an aromatic ring in a (meth) acrylate copolymer in a solvent in the presence of a catalyst in which palladium is supported on zirconium oxide.   The manufacturing method according to claim 1, wherein the total light transmittance of the hydrogenated polymer measured by a method defined in JIS K7105 is 90% or more.   The production method according to claim 1, wherein the copolymer has a weight average molecular weight of 10,000 to 1,000,000.   The production method according to claim 1, wherein the hydrogenation rate of the aromatic ring is 70% or more.   2. The production method according to claim 1, wherein the (meth) acrylate monomer comprises 80 to 100 mol% of alkyl methacrylate and 0 to 20 mol% of alkyl acrylate, and the aromatic vinyl monomer is styrene.   2. The hydrogenated polymer according to claim 1, wherein the weight average molecular weight of the polymer containing an unhydrogenated aromatic ring in the obtained hydrogenated polymer is 1.5 times or less of the weight average molecular weight of the copolymer before hydrogenation. Manufacturing method.   The production method according to claim 1, wherein the amount of palladium supported on the catalyst is 0.01 to 50 wt% with respect to zirconium oxide.   The production method according to claim 1, wherein the solvent is a carboxylic acid ester.   The production method according to claim 1, wherein the precursor of palladium is palladium acetate, palladium chloride, or palladium nitrate.   A hydrogenated polymer obtained by the production method according to claim 1.   An optical material composition comprising the hydrogenated polymer according to claim 10.