NZ506318A

NZ506318A - Methacrylic resin board used for producing bathtubs and basins

Info

Publication number: NZ506318A
Application number: NZ506318A
Authority: NZ
Inventors: Tomohiro Mizumoto; Satoshi Honda; Masashi Mori
Original assignee: Sumitomo Chemical Co
Priority date: 1999-08-20
Filing date: 2000-08-14
Publication date: 2002-02-01
Also published as: AU5346800A; AU773365B2; FR2797634B1; DE10040429A1; FR2797634A1; KR20010050127A

Abstract

Methacrylic resin board is provided for producing sanitary articles such as a bathtub and a washing bowl, having an elongation at break of from 700% to 1000% and a creep index greater than 1x106 Pa. The resin board comprises 5 to 35 parts by weight of a methyl methacrylate based polymer having a viscosity average molecular weight of 50 000 to 300 000, 65 to 95 parts by weight of a methyl methacrylate based monomer, 0.1 to 0.5 part by weight of a polyfunctional monomer copolymerisable with the methyl methacrylate based monomer, and 0.01 to 0.3 part by weight of a chain transfer agent having an alkyl mercaptan content of greater than 80% by weight. The molar ratio of the alkyl mercaptan contained in the chain transfer agent to the polyfunctional monomer is 1.5 to 3.5.

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number 506318 NEW ZEALAND PATENTS ACT, 1953 No: Date: COMPLETE SPECIFICATION METHACRYLIC RESIN BOARD USED FOR PRODUCING SANITARY GOODS AND PROCESS FOR PRODUCING SAID BOARD We, SUMITOMO CHEMICAL COMPANY, LIMITED, a Japanese corporation of 5-33, Kitahama 4-chome, Chuo-ku, Osaka 541-8550, Japan, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - 1 - (followed by page la) intellectual property office OF NZ H AUG 2000 RECEIVED METHACRYLIC RESIN BOARD USED FOR PRODUCING SANITARY GOODS AND PROCESS FOR PRODUCING SAID BOARD Field of the Invention The present invention relates to a methacrylic resin board used for producing sanitary goods such as a bathtub and a washing bowl, and a process for producing said resin board. Background of the Invention JP-A 8-3224 discloses a process for producing a methacrylic resin board used for producing sanitary goods, which comprises the steps of (1) dissolving 5 to 50 parts by weight of a methacrylic resin having a viscosity average molecular weight of about 10,000 to 300,000 in 100 parts by weight of a methacrylic monomer to obtain a syrup like product, and (2) pouring the syrup like product into a cell, followed by polymerization to obtain a methacrylic resin board. As a process for producing sanitary goods from the methacrylic resin board produced by the above process, it is known that the methacrylic resin board is subjected to thermoforming such as vacuum forming and pressure forming to obtain a methacrylic resin article having a desired form, and thereafter is subjected to backing said article with a glass fiber-containing unsaturated polyester resin to reinforce said article. However, the above-mentioned methacrylic resin board has a problems such that the methacrylic resin article is apt to la peel from the glass fiber-containing unsaturated polyester resin, because the methacrylic resin article is stretched during the backing to become thin in its thickness, and the article so stretched has a tendency to recover its original shape, particularly when the article backed with said polyester resin is used as sanitary goods such as a bathtub, which is placed under the condition of contact with hot water alternately with drying up, repeatedly. Incidentally, when such a peeling occurs, the sanitary goods are not only deteriorated in their appearance but also decreased in their strength. Summary of the Invention It is an object of the present invention to provide a methacrylic resin board used for producing sanitary goods, which board has a superior resistance against peeling from a glass fiber-containing unsaturated polyester resin, even when backed with the glass fiber-containing unsaturated polyester resin, and which board has a superior moldability. It is another object of the present invention to provide a process for producing the above-mentioned methacrylic resin board. The present inventors have undertaken extensive studies to obtain a methacrylic resin board, which does not have the above-mentioned problem. As a result, it has been found that (1) a methacrylic resin board having a specific elongation at break and a specific creep index does not have the above-mentioned problem, and (2) a methacrylic resin board, which is 2 31 produced by polymerization of a mixture comprising (i) a specific amount of a methyl methacrylate based polymer having a specific viscosity average molecular weight, (ii) a specific amount of a methyl methacrylate based monomer, (iii) a specific amount of a polyfunctional monomer copolymerizable with said methyl methacrylate based monomer and (iv) a specific amount of a chain transfer agent, does not have the above-mentioned problem. Thereby, the present invention has been obtained. The present invention provides a methacrylic resin board used for producing sanitary goods, which board has an elongation at break of from not less than 700% to 1,000% and a creep index of not more than 1X106 Pa. The present invention also provides a process for producing a methacrylic resin board used for producing sanitary goods, which process comprises the steps of: (i) mixing (a) 5 to 35 parts by weight of a methyl methacrylate based polymer having a viscosity average molecular weight of 50,000 to 300,000, (b) 65 to 95 parts by weight of a methyl methacrylate based monomer, (c) 0.1 to 0.5 part by weight of a polyfunctional monomer copolymerizable with said methyl methacrylate based monomer, and (d) 0.01 to 0.30 part by weight of a chain transfer agent having an alkyl mercaptan content of not less than 80% by weight and a molar ratio of said alkyl mercaptan contained in the chain transfer agent to said polyfunctional monomer of 1.5 to 3.5, thereby obtaining a mixture, provided that a total weight of the methyl methacrylate based polymer and the methyl methacrylate based monomer is INTELLECTUAL PROPERTY OFFICE OF N.Z. 3 2 0 NOV 2001 received j assigned to be 100 parts by weight, and respective proportions of the polyfunctional monomer and the chain transfer agent defined above are based on said 100 parts by weight; (ii) pouring the mixture into a cell; (iii) subjecting the mixture poured into the cell to polymerization; and (iv) taking out the resulting resin board from the cell. Detailed Explanation of the Invention In the present invention, the term "sanitary goods" means appliances for water-using places (for example bathroom, washing room and kitchen) such as a bathtub, a washing bowl, a part of a washing stand, a material for a unit bath and a kitchen utensil. The term "methacrylic resin board" means a plate like product made from a resin, which resin comprises a structural unit derived from a methyl methacrylate monomer as a main structural unit. As said methacrylic resin board, the resin board produced by the above-mentioned process is preferred. A size or thickness of the resin board is not limited, and can be optionally determined depending upon a size of sanitary goods. Usually, a thickness thereof is about 0.1 to about 30 mm. The term "elongation at break" in the present invention means that measured at 160 "C by a tension test according to JIS K-7113, a detailed explanation of which is as given hereinafter. Incidentally, said measuring temperature corresponds approximately to that at which temperature the 4 methacrylic resin board in accordance with the present invention is subjected to thermoforming. The elongation at break of the methacrylic resin board used for producing sanitary goods in accordance with the present invention is so high, namely not less than 700%, and preferably not less than 800%, that the resin board can be easily formed into a deep drawn article such as a bathtub. The term "creep index" in the present invention means a time- T) slope value (Pa) measured by a creep measurement, a detailed explanation of which is as given hereinafter. Since the creep index of the methacrylic resin board in accordance with the present invention is not more than lXio6Pa, the formed methacrylic resin board hardly recover its original shape, that is, the resin board has superior peeling resistance. The term "stress relaxation index" in the present invention means an index measured by stress relaxation measurement (a detailed explanation of the measuring method is as given below) . The stress relaxation index of the methacrylic resin board in accordance with the present invention is preferably not more than 0.07, more preferably not more than 0.035, and so the formed methacrylic resin board can be more rapidly relieved of a residual strain. Namely, the resin board is superior in its peeling resistance. A process for producing the methacrylic resin board used for producing sanitary goods in accordance with the present invention is not particularly limited. As an example of preferred processes, the above-mentioned process is enumerated. intellectual property i office of n.7 ( 5 (followed by page 5a) 2 0 NOV 2001 received ; The term "methyl methacrylate based polymer" used in the present invention means a methyl methacrylate homopolymer or a copolymer of methyl methacrylate with a comonomer copolymerizable therewith. Examples of said comonomer copolymerizable with methyl methacrylate are acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, cyclohexyl acrylate 5a and phenyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, cyclohexyl methacrylate and phenyl methacrylate; methacrylic acid; maleic anhydlide; styrene; cyclohexylmaleimide; acrylonitrile; and polyfunctional monomers having two or more radically polymerizable groups in its molecule such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol methacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, hexanediol diacrylate, hexanediol dimethacrylate, nonanediol diacrylate, nonanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane dimethacrylate, bis(2- methacroyloxyethyl)phthalate, and allyl methacrylate. It is permitted to use two or more of these comonomers at the same time. The comonomer used can be appropriately selected depending upon the forming conditions of the methacrylic resin board to be produced, and purposes of uses thereof. When a particularly superior peeling resistance is required for the methacrylic resin board to be produced, it is preferable to decrease the amount of the monofunctional comonomer used, or to increase the amount of the polyfunctional comonomer used. Further, when a particularly superior moldability is required for the methacrylic resin board to be produced, it is preferable to increase the amount of the monofunctional comonomer used. or to decrease the amount of the polyfunctional comonomer used. The comonomer is used in an amount of preferably 0.5 to 15% by weight, and more preferably 0.5 to 12% by weight, provided that a total weight of methyl methacrylate and the comonomer used is assigned to be 100% by weight. When the amount of the comonomer used is beyond said range, the moldability and the peeling resistance of the methacrylic resin board produced are apt to deteriorate. The term "viscosity average molecular weight" of the methyl methacrylate based polymer used in the present invention means a molecular weight "M" calculated by the following formula (1). In M = {In [77] - In (4.8X10"5)} / 0.8 (1) wherein M is a viscosity average molecular weight, and [ 7] ] is a limiting viscosity number measured by using Ubbelohde's viscometer. The viscosity average molecular weight of the methyl methacrylate based polymer is from 50,000 to 300,000. When said molecular weight is less than 50,000, the peeling resistance of the methacrylic resin board produced is apt to deteriorate, whereas, when said molecular weight exceeds 300,000, the moldabilty of the methacrylic resin board produced is apt to deteriorate. The methyl methacrylate based polymer is used in an amount of 5 to 35 parts by weight based on 100 parts by weight of a 7 total of the methyl methacrylate based polymer and the methyl methacrylate based monomer. When said amount is less than 5 parts by weight, the peeling resistance of the methacrylic resin board produced is apt to deteriorate. Whereas, when said amount exceeds 35 parts, a viscosity of the mixture prepared in the above step (i) becomes too high to handle the mixture, and moreover, the moldabilty of the methacrylic resin board produced is apt to deteriorate. The term "methyl methacrylate based monomer" means a mixture comprising a methyl methacrylate monomer in a predominant amount and a comonomer copolymerizable with said methyl methacrylate monomer. A proportion of the comonomer in the methyl methacrylate based monomer is not limited. It is preferable to use a mixture, wherein the comonomer is contained in an amount of 0.5 to 15 parts by weight in the 65 to 95 parts by weight of the methyl methacrylate based monomer. When the proportion of the comonomer is too small, the moldability of the methacrylic resin board produced is apt to deteriorate, and when it is too large, the peeling resistance of the methacrylic resin board produced is apt to deteriorate. Examples of the comonomer copolymerizable with the methyl methacrylate monomer are acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, cyclohexyl acrylate and phenyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, isononyl 8 methacrylate, cyclohexyl methacrylate and phenyl methacrylate; methacrylic acid; maleic anhydlide; styrene; cyclohexylmaleimide; and acrylonitrile. Among them, acrylic acid esters are particularly preferred. It is permitted to use two or more of these comonomers at the same time. A process for preparing the mixture obtained in the step (i) is not limited. It is preferable to use a process, wherein the polyfunctional monomer and the chain transfer agent are added to a mixture (hereinafter, said mixture being simply referred to as "syrup" ) of the methyl methacrylate based polymer and the methyl methacrylate based monomer. A process for preparing the syrup is not also limited. For example, a conventional process, wherein the methyl methacrylate based polymer is mixed with and dissolved in the methyl methacrylate based monomer, may be used. In order to increase solubility of the methyl methacrylate based polymer in the methyl methacrylate based monomer, it is preferable to use a methyl methacrylate based polymer in a powder form having an average particle size of about 0.1 Mm to about 1 mm, or a pellet form having an average particle size of not more than 10 mm. As another process for preparing the syrup, there can be enumerated a process, wherein a mixture of the methyl methacrylate monomer and a radical polymerization initiator is heated to polymerize a part of said monomer. The term "polyfunctional monomer" used in the present invention means a monomer having at least two radically polymerizable groups in its molecule, which monomer is copolymerizable with the methyl methacrylate based monomer. Examples of the polyfunctional monomer are ethylene glycol diacrylate, ethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, hexanediol diacrylate, hexanediol dimethacrylate, nonanediol diacrylate, nonanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane dimethacrylate, bis(2-methacroyloxyethyl)phthalate, and allyl methacrylate. Among them, neopentyl glycol dimethacrylate and neopentyl glycol diacrylate are particularly preferred. It is permitted to use two or more of these polyfunctional monomers at the same time. The polyfunctional monomer is used in an amount of 0.1 to 0.5 part by weight based on 100 parts by weight of the above-mentioned syrup. When the amount is less than 0.1 part by weight, a cross-linking structure of the resin board obtained is apt to be insufficient, and as a result, the peeling resistance of the methacrylic resin board produced is apt to deteriorate. Whereas, when it exceeds 0.5 part by weight, the cross-linking structure of the resin board obtained is apt to be too dense, and as a result, the moldability of the methacrylic resin board produced is apt to deteriorate. Examples of the chain transfer agent used in the present invention are alkyl mercaptans such as lauryl mercaptan, octyl mercaptan and butyl mercaptan; thioglycolic acid esters such as 2-ethylhexyl thioglycolate and ethyl thioglycolate; j3 -mercaptopropionic acid esters such as octyl 3 10 mercaptopropionate; j3 -mercaptopropionic acid; and aromatic mercaptans such as thiophenol and p(t-butyl) thiophenol. Among them, alkyl mercaptans are preferred. It is permitted to use two or more of the chain transfer agents at the same time. From a viewpoint of the peeling resistance, it is preferred to use the chain transfer agent comprising the alkyl mercaptan in an amount of not less than 80% by weight. The chain transfer agent is used in an amount of 0.01 to 0.30 part by weight based on 100 parts by weight of the syrup. When said amount is less than 0.01 part by weight, the moldability of the methacrylic resin board produced is apt to deteriorate. Whereas, when it exceeds 0.30 part by weight, the peeling resistance of the methacrylic resin board produced is apt to deteriorate. A molar ratio of the alkyl mercaptan contained in the chain transfer agent to the polyfunctional monomer is 1.5 to 3.5, whereby the methacrylic resin board in accordance with the present invention can have both the superior moldability and the superior peeling resistance. In carrying out the polymerization by adding the polyfunctional monomer and the chain transfer agent to the syrup, a radical polymerization initiator is added to the syrup. The radical polymerization initiator is not limited in its kind, and those usually used for producing methacrylic resin boards may be used. Specific examples thereof are peroxide initiators such as lauroyl peroxide, benzoyl peroxide, di-t-butyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxy isobutylate, t-butylperoxy pivalate, t-butylperoxy benzoate, t-butylperoxy 11 acetate, diisopropylperoxy dicarbonate and di-sec-butylperoxy dicarbonate; azo initiators such as 2,2'-azobisisobutylonitrile and 2,2'-azobis(2,4- dimethylvaleronitrile); and redox initiators comprising a combination of the peroxide initiator and a reductive compound such as amines and mercaptans as a main component. These radical polymerization initiators may be used in an amount of about 0.0001 to about 5 parts by weight based on 100 parts by weight of the syrup. Respective components used in the step(i) may be used in combination with additives such as antioxidants, ultraviolet-ray absorbers, mold releasing agents, dyes, pigments and inorganic fillers, depending upon uses of the methacrylic resin board in a manner such that the objects of the present invention are by no means impaired. A preferred mold releasing agent is that comprising a phosphoric acid ester represented by the following formula (2) in an amount of not less than 50% by weight, {r1-(r20)n}m-p(0)-(0h)3-i„ (2) wherein Ri and R2 are independently of each other an alkyl group having 1 to 20 carbon atoms, m is 1 or 2, and n is a number average of 0 to 100. As the cell used in the step (ii), there are exemplified (a) a cell constituted with two glass plates or two metal plates, a soft sealant and a clump, and (b) a continuous cell constituted 12 with two stainless steel-made belts. A cell thickness can be determined so as to obtain a desired resin board, and is usually within a range of about 0.1 to about 30 mm. The polymerization in the step (iii) is carried out according to a conventional polymerization method so-called a cell casting method. The polymerization can be carried out by heating the cell with use of a heating source such as a hot wind, hot water and an infrared heater. A polymerization temperature and a polymerization time may be appropriately determined depending upon the kind and an amount of the polymerization initiator, and the composition of the mixture obtained in step (i) . The polymerization can be usually carried out at 50 to 120"C for one hour to several ten hours. In step (iv), the resulting resin board can be taken out by taking the cell to pieces. If desired, the methacrylic resin board used for producing sanitary goods in accordance with the present invention can be used in the form of a laminate with resins known in the art such as an ABS resin and a urethane resin. According to the present invention, a methacrylic resin board used for producing sanitary goods, which board has a superior peeling resistance and a superior moldability, can be produced stably and easily. Said resin board can be easily formed into deep drawn sanitary goods such as a bathtub and a washing bowl, because the board has a low tensile strength and a high elongation at break in thermoforming. 13 Example The present invention is illustrated in more detail with reference to the following Examples, which are only illustrative, and are not limitative for the scope of the present invention. 1. Tensile test Elongation at break (%) was measured according to JIS K-7113 by using a test specimen having a shape similar to that of JIS No. 2 test specimen, except that (a) a distance between marked lines was 15 mm and (b) a sample thickness was 5 mm, by pre-heating the test specimen at 160t, and by carrying out the tensile test under a condition of a cross head speed of 500 mm/min. 2. Measurement of creep Using a viscoelasticity measuring apparatus (Type SR-5000) made by Rheometric Scientific Co., a creep index (time-77 slope value (Pa)) was measured according to the following steps (i) to (vi): (i) cutting a methacrylic resin board of 5 mm thickness to obtain a circular sample of 25 mm$ ; (ii) setting the sample to a measuring instrument (parallel plate of 25 mm<f> ) kept at ISO'C, leaving it for 15 minutes, and then confirming that the sample reaches 180*0; (iii) applying stress ( O ) of 15,000 Pa to the sample in 14 a rotation direction for 500 seconds, and then removing said stress; (iv) obtaining a creep compliance J(t)(= T (t)/0 ) from a time variation 7(t) of strain; (v) plotting a shear viscosity 7? (t) (a reciprocal number of time differential value of time-J(t)) for every time to obtain a straight line; and (vi) defining an initial slope of said straight line as the time-77 slope value (Pa). The larger the time- 77 slope value of the methacrylic resin board, the larger the tendency to recover its original shape prior to applying stress, namely inferior the peeling resistance thereof. 3. Measurement of stress relaxation Using a viscoelasticity measuring apparatus (Type RDA-2) made by Rheometric Co., the stress relaxation index was measured according to the following steps (i) to (vii): (i) preparing a resin-made sample having a size of 5 mm thickness, 3 mm width and 55 mm length; (ii) setting the sample to a dual cantilever measuring instrument so as to make a measuring length about 3.8 mm; (iii) raising a measuring temperature to 80"C, leaving the sample for 10 minutes, and then confirming that the sample reaches 80X^; 15 (iv) applying strain of 1% to the sample for 37 minutes in a rotation direction, and then obtaining a relationship between time and relaxation modulus of elasticity from the generated stress; (v) repeating the above steps, except that the measuring temperature is changed to 90*0 and 95^ to obtain respective relationship between time and relaxation modulus of elasticity at those temperature; (vi) obtaining a relationship between a time period of lXio5 seconds and relaxation modulus of elasticity at 80"C from respective relationships between time and relaxation modulus of elasticity obtained at 80 *C , 90 "C and 95 by using a time-temperature overlapping principle provided that a standard temperature is assigned to be 80*0; and (vii) dividing the thus obtained relaxation modulus, G( 2), of elasticity after lXio5 seconds by the relaxation modulus, G(l), of elasticity after 0.05 second to obtain a stress relaxation index, G(2)/G(l). 4. Evaluation of moldability Evaluated according to the following steps (i) to (iii): (i) setting a mold to a vacuum forming apparatus equipped with a sliding infrared heater, wherein the mold can form a square box, and has a square base of 280mmX280mm corresponding to the bottom of the box, and depth of 70 mm corresponding to the side of the box, and a curvature radius of 5 mm between the 16 bottom and the side; (ii) setting a resin-made sheet on the mold; and (iii) heating the surface of the sheet to 180*0, and then subjecting the sheet to vacuum forming. O : a box having a desired shape was obtained. X : a box having a desired shape was not obtained. 5. Evaluation of peeling resistance Peeling resistance was evaluated according to the following steps (i) to (viii): (i) fixing a methacrylic resin board of 270 mm length, 220 mm width and 5 mm thickness to a fixing flame; (ii) heating the resin board with a far infrared heater until the surface temperature of the resin board reaches 200"C; (iii) subjecting the heated resin board to push up molding; (iv) two minutes after pushing up, cooling the whole of the formed article forcibly for 5 minutes with a spot cooler; (v) measuring a height of pushing up, which height means a length between the bottom and the inside of the fixing flame, using a 5 mm unit measure, and defining said height as a mold height (H0); (vi) dipping the formed article in hot water of 90*C for five days, and then measuring a mold height (Hi) in a manner similar to that mentioned above; 17 (vii) calculating a reverting ratio in push up molding according to the following formula (3); and Reverting ratio in push up molding(%) = (H0-Hi) X100/H0 (3) (viii) regarding an article having a reverting ratio in push up molding of not more than 30% as an article superior in peeling resistance (which is marked with O), and the article having a reverting ratio in push up molding of more than 30% as an article inferior (which is marked with X ). Example 1 (i) 25 Parts by weight of a methyl methacrylate based polymer having a viscosity average molecular weight of 130, 000, which had been produced by subjecting 95.0% by weight of methyl methacrylate and 5 . 0% by weight of methyl acrylate to suspension polymerization, (ii) 70.5 parts by weight of a methyl methacrylate monomer, (iii) 4.5 parts by weight of 2-ethylhexyl acrylate, (iv) 0.18 part by weight of neopentyl glycol dimethacrylate (polyfunctional monomer), (v) 0.06 part by weight of lauryl mercaptan (chain transfer agent), (vi) 0.1 part by weight of 2,2'-azobisisobutylonitrile (polymerization initiator), and (vii) 0.01 part by weight of a mold releasing agent, PHOSPHANOL RS 710 (trade name) manufactured by Toho Chemical Industry Company, Limited, were mixed to obtain a mixture. Here, the above-mentioned (ii) methyl methacrylate monomer and (iii) 2-ethylhexyl acrylate correspond to the methyl methacrylate based monomer in accordance with the present invention. A molar ratio of the above-mentioned polyfunctional monomer to lauryl mercaptan was 2.5. The mixture was subjected to degasification, and thereafter poured into a cell of 5 mm thickness constituted with two glass plates and a vinyl chloride resin-made gasket. The mixture poured into the cell was kept at 65*C for four hours and additionally at 120 "C for one hour to complete polymerization, and thereafter the resin board produced was taken off from the cell, thereby obtaining a methacrylic resin board. Tests results of the resin board are as shown in Table 2. Examples 2, 3 and 5 to 8, and Comparative Examples land 2 Example 1 was repeated except that the kind and amount of (i) methyl methacrylate based polymer, and respective amounts of (ii) methyl methacrylate monomer, (iii) 2-ethylhexyl acrylate, (iv) polyfunctional monomer and (v) chain transfer agent were changed to those shown in Table 1. Evaluation results thereof are as shown in Table 2. Example 4 Example 1 was repeated except that (iii) 2-ethylhexyl acrylate was changed to butyl acrylate, and (iv) 0.18 part by weight of neopentyl glycol dimethacrylate (polyfunctional monomer) was changed to 0.10 part by weight of ethylene glycol dimethacrylate. Evaluation results thereof are as shown in 19 Table 2. Asterisked numbers 1 to 7 in Table 1 are as follows. *1 MMA : methyl methacrylate *2 MA : methyl acrylate *3 EHA : 2-ethylhexyl acrylate *4 Polyfunctional monomer : neopentyl glycol dimethacrylate *5 Chain transfer agent : lauryl mercaptan *6 Butyl acrylate (in place of EHA) *7 Ethylene glycol dimethacrylate (in place of neopentyl glycol dimethacrylate) 20 Table 1 Methyl methacrylate based polymer Methyl methacrylate based monomer Polyfunctional monomer*4 Chain transfer agent*5 MMA*1 (wt%) MA*2 (wt%) molecular weight part by weight MMA*1 part by weight EHA*3 part by weight part by weight part by weight f Example 1 95.0 5.0 130000 25 70.5 4.5 0.18 0.06 Example 2 95.0 5.0 130000 23 72.4 4.6 0.18 0.06 Example 3 95.0 5.0 130000 25 71.2 3.8 0.18 0.06 Example 4 95.0 5.0 130000 25 70.5 4.5*6 0.10*7 0.06 Example 5 89.5 10.5 140000 25 72.0 3.0 0.18 0.06 Example 6 99.2 0.8 140000 25 70.2 4.8 0.18 0.06 Example 7 97.3 2.7 150000 25 70.7 4.3 0.18 0.06 Example 8 96.0 4.0 110000 25 71.0 4.0 0.18 0.06 Comparative Example 1 96.0 4.0 110000 27 68.2 4.8 0.18 0.04 Comparative Example 2 96.0 4.0 110000 25 71.0 4.0 0.18 0 21 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> Table 2 Elongation at break (%) Creep index X10s(Pa) Stress relaxation index Moldability Peeling resistance Reverting ratio in push up molding (%) Example 1 940 6.9 0.026 o o 27 Example 2 960 8.0 0.025 o o 15 Example 3 1000 8.1 - o o 25 Example 4 1000 6.1 - o o 25 Example 5 940 7.2 - o o 29 Example 6 900 7.8 - o o 21 Example 7 860 7.6 - o o 21 Example 8 800 8.0 - o o 21 Comparative Example 1 780 13.3 o X 41 Comparative Example 2 500 34.1 X impossible to evaluate impossible to mold 22 #«|t > WHAT WE CLAIM IS:

1. A methacrylic resin board used for producing sanitary goods, as defined herein, which board has an elongation at break of from not less than 700% to 1,000% and a creep index of not more than 1X106 Pa.

2. The methacrylic resin board used for producing sanitary goods according to Claim 1, wherein the elongation at break is not less than 800%.

3. The methacrylic resin board used for producing sanitary goods according to Claim 1, wherein the board has a stress relaxation index of not more than 0.07.

4. The methacrylic resin board used for producing sanitary goods according to Claim 2, wherein the board has a stress relaxation index of not more than 0.07.

5. The methacrylic resin board used for producing sanitary goods according to Claim 1, wherein the board has a stress relaxation index of not more than 0.035.

6. The methacrylic resin board used for producing sanitary goods according to Claim 2, wherein the board has a stress relaxation index of not more than 0.035.

7. A process for producing a methacrylic resin board used 23 / 2 0 NOV 2001 I R EC E f Vr n for producing sanitary goods, as defined herein, which process comprises the steps of: (i) mixing (a) 5 to 35 parts by weight of a methyl methacrylate based polymer having a viscosity average molecular weight of 50,000 to 300,000, (b) 65 to 95 parts by weight of a methyl methacrylate based monomer, (c) 0.1 to 0.5 part by weight of a polyfunctional monomer copolymerizable with said methyl methacrylate based monomer, and (d) 0.01 to 0.30 part by weight of a chain transfer agent having an alkyl mercaptan content of not less than 80% by weight and a molar ratio of said alkyl mercaptan contained in the chain transfer agent to said polyfunctional monomer of 1.5 to 3.5, thereby obtaining a mixture, provided that a total weight of the methyl methacrylate based polymer and the methyl methacrylate based monomer is assigned to be 100 parts by weight, and respective proportions of the polyfunctional monomer and the chain transfer agent defined above are based on said 100 parts by weight; (ii) pouring the mixture into a cell; (iii) subjecting the mixture poured into the cell to polymerization; and (iv) taking out the resulting resin board from the cell.

8. The process for producing a methacrylic resin board used for producing sanitary goods according to Claim 7, wherein the methyl methacrylate based polymer comprises a copolymer having a structural unit derived from a methyl methacrylate monomer and a structural unit derived from an acrylic acid ester, and 24 intellectual property office of n.z. 2 0 NOV 2001 DCPCIUtn having a content of the structural unit derived from the acrylic acid ester of not less than 0.5% by weight, provided that a total weight of the structural unit derived from the methyl methacrylate monomer and the structural unit derived from the acrylic acid ester is assigned to be 100% by weight.

9. The process for producing a methacrylic resin board used for producing sanitary goods according to Claim 7, wherein the methyl methacrylate based monomer in an amount of 65 to 95 parts by weight contains an acrylic acid ester in an amount of 0.5 to 15 parts by weight.

10. The process for producing a methacrylic resin board used for producing sanitary goods according to Claim 7, wherein the polyfunctional monomer comprises neopentyl glycol diacrylate or neopentyl glycol dimethacrylate.

11. Sanitary goods, as defined herein, which comprise the methacrylic resin board according to Claim 1.

12. Sanitary goods, as defined herein, which comprise the methacrylic resin board produced by the process claimed in Claim 7.

13. A process for producing a methacrylic resin article having a desired form for sanitary goods, as defined herein, which process comprises the steps of: 25 INTELLECTUAL PROPERTY OFFICE OF N.Z. 2 0 NOV 2001 received (i) shaping the methacrylic resin board according to any one of Claims 1 to 6 into a methacrylic resin article in a thermoforming method; and (ii) backing the article with a glass fibre-containing unsaturated polyester resin to reinforce the article.

14. A process for producing a methacrylic resin article having a desired form for sanitary goods, as defined herein, which process comprises the steps of: (i) shaping the methacrylic resin board produced by the process according to any one of Claims 7 to 10 into a methacrylic resin article in a thermoforming method; and (ii) backing the article with a glass fibre-containing unsaturated polyester resin to reinforce the article.

15. Use of the methacrylic resin board according to Claim 1 for producing sanitary goods, as defined herein.

16. Use of the methacrylic resin board produced by the process claimed in Claim 7 for producing sanitary goods, as defined herein.

17. Use according to Claim 15 or 16, substantially as herein described.

18. A process according to claim 13 or 14, substantially as herein described. 26 2 0 NOV 2001 RECEIVED

19. Sanitary goods, as defined herein, whenever produced according to the process of Claim 13, 14 or 18 or the use of Claim 15, 16 or 17.

20. A methacrylic resin board, substantially as herein described with reference to Examples 1-8.

21. A process for producing a methacrylic resin board, substantially as herein described with reference to Examples 1-8.

22 . A methacrylic resin board whenever produced according to the process of any one of Claims 7-10 and 21. intellectual property office of n.z. 2 0 NOV 2001 received 27 </div>