United States Patent Office Patented July 22, 1969
Total Page：16
File Type：pdf, Size：1020Kb
3,457,233 United States Patent Office Patented July 22, 1969 2 3,457,233 by copolymerization, so the resistance to degradation or PROCESS FOR PREPARNG POLYOXY. thermal stabilization is achieved. Further, the thermal METHYLENE COPOLYMERS stability of polyoxymethylene copolymer is remarkably Shinichi Ishida, Horomichi Fukuda, and Shizuko Saito, improved by treating said copolymer with an amine, am Tokyo, Japan, assignors to Asahi Kasei Kogyo Kabu monia, hydrazine, urea or derivatives thereof, without shiki Kaisha, Osaka, Japan, a corporation of Japan adversely influencing the original excellent physical prop No Drawing. Fied Dec. 23, 1964, Ser. No. 420,789 erties such as high tenacity and processability of polyoxy Clains priority, application Japan, Dec. 28, 1963, methylene copolymer. 38/70,493, 38/70,494; Jan. 13, 1964, 39/1,144 Int, C. C08g 1/18, 1/22 The unsaturated dibasic aliphatic carboxyanhydride ac U.S. C. 260-73 O Claims cording to the present invention includes maleic anhy O dride, itaconic anhydride, monochloro maleic anhydride and the like. The amount of said anhydride usually equals to 0.01-20% by weight of trioxane. It is still desirable AESTRACT OF THE DESCLOSURE to determine the Suitable amount according to the kind of A process for producing a polyoxymethylene copoly applied acid anhydride. mer which can be used for the production of moldings 5 The copolymerization according to the present inven having excellent properties, such as superior whiteness and tion is carried out by the irradiation of ionizing rays or thermal stability. The process comprises copolymerizing in the presence of a catalyst. It has been well-known that trioxane With at least one unsaturated aliphatic di only trioxane in solid phase is polymerized by irradiation carboxylic acid selected from the group consisting of 20 of the ionizing rays, and the present invention employs maleic anhydride, itaconic anhydride, and monochloro the conventional well-known process. maleic anhydride under the influence of an ionizing radia In the polymerization in solid phase, the acid anhydride tion or a catalyst, and then preferably, reacting the re is copresent with trioxane in the form of a mixture or Sulting copolymer with at least one agent selected from a Solid Solution. A process for obtaining the state of co the group consisting of amines, ammonia, hydrazine, 25 existence is, for example, a mixing obtained by simple phenylhydrazine, urea, ethyleneurea, diethylurea and di addition, fusing or using a solvent, but is not limited phenylurea. thereto, Two different processes are available for the polymeriza tion carried out by irradiation of the ionizing ray, that The present invention relates to a process for prepar 30 is, irradiation polymerization and after-effect (post) ing highly thermostable polyoxymethylene copolymers. polymerization by previous irradiation. In the case of the The object of the present invention is to prepare polyoxy former, the polymerization is started as soon as the ir methylene copolymers which are available for the pro radiation is applied at a temperature from room temper duction of moldings having excellent properties such as ature to 100° C. In case of the latter, the previous irradi Superior whiteness and thermal stability. 35 tion is carried out at a temperature from the temperature It has been known that polyoxymethylenes which have of a liquid nitrogen bath to room temperature and, after reCurrent units of -CH2O- are prepared by polymeriz finishing the irradiation, the polymerization is carried out ing anhydrous formaldehyde by using a catalyst such as by heating at a temperature from 30° C. to the melting amines, onium Salts, or organometallic compounds or light point of the polymerization mixture. or ionizing rays in the presence or absence of an organic 40 The ionizing rays effective for polymerization are ox-ray, Solvent, by polymerizing trioxane i.e., the cyclic trimer of (3-ray, y-ray and X-ray, and preferable is the irradiation of formaldehyde in the presence of a catlyst such as antimony van de Graaff and y-ray irradition from the source of trifluoride or boron trifluoride, or by subjecting trioxane cobalt 60 with respect to convenience and easiness in prac to irradiation of ionizing rays in the solid phase. How tice. The irradiation amount is not especially limited, but ever, the molded products of thus obtained polyoxy an excess of irradiation is not desirable, because it causes methylene are unsatisfactory in the thermal stability. the breakdown of the polymer chain. The dose rate is The present inventors were successful in the prepara not limited in particular. tion of polyoxymethylene copolymers containing a small The copolymerization according to the present inven amount of an acid anhydride group, by polymerizing tri tion can be carried out not only by the action of the oxane under the irradiation of ionizing rays or in the ionizing ray but also various catalysts. For example, a presence of a catalyst in the copresence of unsaturated 50 suitable catalyst for the polymerization of trioxane in aliphatic dicarboxyanhydride, and further have found that cludes boron trifluoride, complexes thereof, antimony said polyoxymethylene copolymers containing these acid fluoride, Sulfonic acid, Sulfonate and the like, or in case anhydride groups can be treated in the copresence of of using said acid anhydride, there may be employed a amines, ammonia, hydrazine, urea or derivatives thereof very effective radical initiator of the peroxide type such under gentle conditions, to obtain nitrogen-containing 55 as benzyl peroxide, lauryl peroxide, dibutyl peroxide, di polyoxymethylene copolymers of much improved thermal chlorobenzoyl peroxide, acetyl peroxide, methyl ethyl stability. ketone peroxide, cumene hydroperoxide and the like. The chains of polyoxymethylenes are decomposed due In the copresence of 0.01% to 5% by weight of said to heat, and most of this decomposition consist of degrada catalyst, in the absence or the presence of a solvent, the tion starting from the end of the chain. Therefore, when 60 polymerization is carried out by heating at a temperature the chain of polyoxymethylene has a heterogeneous unit from 30 C, to 120 C. group or structure interrupting the depolymerization, the A more desirable result, however, has usually been ob thermal stability of polyoxymethylene is increased. tained in polymerization with irradiation. The chain of polyoxymethylene, according to the pres The polymers thus obtained are washed and extracted ent invention, has a cyclic acid anhydride unit introduced 65 With a Suitable solvent such as acetone, to remove the 3,457,233 3 4. unreacted monomer and individual polymer of said acid EXAMPLE 2 anhydride, and elementary analysis, infrared absorption, spectrum analysis and chemical detection have proved 9 g. of trioxane crystals and 1 g, of maleic anhydride that said acid anhydride group is included in the structure are well mixed and fused, degasified at -20° C., subjected of polyoxymethylene. to 2.45x 106 of y-irradiation at 50° C. in an ampule with The polymer obtained according to the present inven 5 y-rays of 5.1 x 104 rad./hr. in dose rate from a 400 curie tion is superior in whiteness and reaches a high degree of cobalt-60 source, extracted with acetone by opening the polymerization by selecting a suitable condition. ampule and dried. The yield was 75 g. The produce had a Furthermore, polyoxymethylenes of high moldability melting point of 160° C. and a specific viscosity of 1.80 are obtained by esterification or etherification or other in a 1% solution of p-chlorophenol. protection of the chain ends. O 5 g. of the obtained polyoxymethylene copolymer were For increasing the thermal stability, the cyclic acid an added with 30 cc. of an aqueous solution of hydrazine, hydride group of said polyoxymethylene copolymer is kept at 50° C. for 3 hours and cleansed with ether and reacted with an amine, ammonia, hydrazine, a derivative alcohol, and dried. The yield was 4.96 g. The thermal thereof, urea or a derivative thereof, and the polyoxy decomposition rate of this product was 0.16%/min. at methylene copolymer thus obtained contains an amide or 222 C. imide group in case of using an amine, an amide group EXAMPLE 3 in the case of ammonia, and a hydrazide group in case of Introducing 3 g. of the polyoxymethylene copolymer hydrazine. obtained as described in Example 1 into 30 cc. of liquid The suitable treating agent according to the present in ammonia, reacting the mixture at 100° C. for 20 hours in vention includes primary or secondary, aliphatic or aro an autoclave, and distilling off liquid ammonia, the ob matic amines, such as methylamine, ethylamine, propyl tained product was cleansed with benzene and dried. The amine, butylamine, pentylamine, hexylamine, cyclohexyl yield was 2.95 g. The infra-red ray absorption spectrum amine, octylamine, nonylamine, aniline, toluidine, naph proved the presence of amido group and the absence of thylamine, dimethylamine, dipropylamine, dibutylamine, acid anhydride. The thermal decomposition rate of this dihexylamine, dioctylamine, N-methylaniline, ethylene product (K. 222) was 0.18%/min. at 222 C. imine, propyleneimine, p-aminobenzamide and the like, EXAMPLE 4. ammonia, hydrazine, urea and derivatives thereof such 10 g. of trioxane crystals and 0.5 g. of itaconic anhy as phenylhydrazine, ethyleneurea, diethylurea, diphenyl dride are well mixed and fused, degasified at -20° C., urea, which are used under anhydrous condition or in the 30 subjected to 1.2 x 106 of y irradiation at 0° C. in an form of solution. ampule with y rays of 5.1 x 104 rad./hr. from a 400 curie The process of the persent invention is carried out by cobalt-60 source and heated at 50° C. for 8 hours in a using said treating agent below room temperature or under water bath. The contents were taken out by opening the heating.