JP2005008891A - Crosslinked polymer and medical sheet comprising the polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crosslinked polymer having proper viscoelasticities in molten state and in solid state respectively and useful as a material of a sheet for radiation therapy, a sheet for plaster cast, a patterning sheet for wig, tooth or the like. <P>SOLUTION: The crosslinked polymer is obtained by irradiating a polytransisoprene resin or an ethylenic copolymer resin each having a melting point of 40-80°C with active energy rays to cause crosslinking. The medical sheet comprises the crosslinked polymer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cross-linked polymer by irradiation with active energy rays and a medical sheet comprising the cross-linked polymer. More specifically, the present invention relates to a crosslinked polymer by irradiation with active energy rays having appropriate viscoelasticity at a relatively low temperature, and a radiation treatment sheet, a cast sheet, and a wig or tooth mold sheet made of the crosslinked polymer.

  Thermoplastic resins having a melting point (softening point) such as polycaprolactone and polyisoprene in the range of 40 to 80 ° C. can be easily melted at a relatively low temperature, and can be easily deformed by applying external force, and cooled and solidified. Then, taking advantage of its toughness, it is used for casting sheets such as casts, wigs and teeth.

  However, since the viscosity of these resins in the molten state is low and there is no elasticity, there is a drawback that “sag” occurs, breaks when excessive external force is applied, or does not return to its original shape once deformed. .

  As a result of the study, the present inventor has found that the resin obtained by irradiating a low melting point thermoplastic resin with an active energy ray to cause a crosslinking reaction has rubber elasticity and shape memory property in a molten state, and various other resins. As a result, the inventors have found that the sheet can be freely formed without causing “sagging” or sheet breakage, and the present invention has been achieved.

  That is, the present invention provides a crosslinked polymer obtained by irradiating an active energy ray to a polytransisoprene resin or ethylene copolymer resin having a melting point of 40 to 80 ° C. to cause a crosslinking reaction. To do.

  The present invention also provides a radiation treatment sheet, a cast sheet, and a wig or tooth shaping sheet comprising the above-mentioned crosslinked polymer.

  Since the crosslinked polymer of the present invention is melted at a relatively low temperature and has appropriate viscoelasticity at the time of melting and solidifying, a radiation treatment sheet, a cast sheet, and a wig or tooth mold sheet It is useful as a material.

  Examples of the polytransisoprene resin or ethylene copolymer resin having a melting point of 40 to 80 ° C. in the present invention include polytransisoprene resin, ethylene-vinyl acetate, ethylene-vinyl chloride, ethylene-vinyl alcohol (ethylene-vinyl acetate). Any resin can be used as long as it has a melting point of 40 to 80 ° C. among the saponified copolymer) and the ethylene-propylene copolymer. A proportion of 10 to 40 mol% of the copolymer component is usually preferable because the melting point is in the range of 40 to 80 ° C.

  Polytransisoprene resins and ethylene copolymer resins are currently produced on a commercial scale and can be preferably used. The ethylene-based copolymer resin has crystallinity, but is excellent in transparency, and is preferably used in applications where transparency is required in a mold sheet such as a wig mold material.

  The number average molecular weight of the polytransisoprene resin or ethylene copolymer resin having a melting point of 40 to 80 ° C. is usually 10,000 to 300,000, preferably 40,000 to 200,000, more preferably. It is in the range of 60,000 to 150,000.

  When the molecular weight is less than 10,000, it is difficult to produce various molded products, and the mechanical strength of the produced products tends to be remarkably lowered. Conversely, when the molecular weight exceeds 300,000, the melt viscosity Is too high, and there is a tendency for molding processability to decrease, which is not preferable.

  The reason why the melting point is 40 to 80 ° C. is that it is difficult to store in the summer in a crosslinked polymer obtained from a temperature lower than 40 ° C., and when used as a fixing sheet, it does not solidify easily even at room temperature. Therefore, it is difficult to use, and in the case of a cross-linked polymer obtained from a polymer having a temperature higher than 80 ° C., the molten resin is hot and cannot be placed on the human body.

  In a preferred embodiment of the present invention, a polyfunctional acrylic monomer and a polyfunctional allyl monomer are added to a polytransisoprene resin or ethylene copolymer resin having a melting point of 40 to 80 ° C. These monomers are not particularly limited, and examples of polyfunctional acrylic monomers include ethylene oxide-modified bisphenol A di (meth) acrylate, 1,4-butanediol di (meth) acrylate, diethylene glycol di ( (Meth) acrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, caprolactone-modified dipentaerythritol hexaacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, polyethylene glycol di (meth) acrylate, trimethylolpropane triacrylate, Ethylene oxide modified trimethylolpropane triacrylate, propylene oxide modified trimethylolpropane triacrylate Examples of polyfunctional allylic monomers include triallyl cyanurate, triallyl isocyanurate diallyl phthalate, tris (acryloxyethyl) isocyanurate, tris (methacryloxyethyl) isocyanurate and mixtures thereof. Examples include diallylbenzene phosphonate and a mixture thereof.

  These polyfunctional acrylic monomers or polyfunctional allyl monomers are used in an amount of 0.1 to 30 parts by weight, preferably 0.3 to 10 parts by weight based on 100 parts by weight of the polytransisoprene resin and the ethylene copolymer resin. Part by weight, more preferably in the range of 0.5 to 5 parts by weight. When the amount is less than 0.1 parts by weight, the shape memory property of the crosslinked polymer is not at a satisfactory level. Conversely, when the amount exceeds 30 parts by weight, the crosslinked polymer becomes too rigid and toughness Is not preferable because of a tendency to decrease.

  The active energy ray is not particularly limited in wavelength and energy amount, but an electron beam (EB) is common. These active energy rays can be irradiated using a known apparatus. The irradiation dose is appropriately selected as an amount sufficient to cause crosslinking in the thermoplastic resin. For example, in the case of an electron beam (EB), an acceleration voltage of 100 to 300 KV and an absorbed dose of 0.1 to 30 Mrad are appropriate.

  When irradiating these active energy rays, there is no particular limitation on the form of the thermoplastic resin having a melting point of 40 to 80 ° C., but a film or sheet having a thickness of 10 μm to 5 mm has high irradiation efficiency. Easy to use. In particular, a sheet having a thickness of about 0.5 mm to 3 mm is preferably used because it can be used as a medical sheet such as a radiation treatment sheet, a cast sheet, a wig, or a tooth shaping sheet.

  In addition, any substance can be mixed or applied to the crosslinked polymer of the present invention at an appropriate time depending on the intended use.

  Examples of the substances include inorganic fillers such as glass fiber, glass beads, metal powder, talc, mica, and silica, pigments, various stabilizers, flame retardants, antistatic agents, antifungal agents, plasticizers, and viscosity imparting agents. Examples thereof include additives, thermoplastic resins, and curable oligomers.

  The restoration rate of the crosslinked polymer obtained as described above is usually 80% or more.

<Example>
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited only to these Examples.
In addition, the measuring method of each physical property is as follows.

1. Breaking strength, strength at 500% elongation and elongation at break: according to JIS K7113. The tensile strength is measured at 23 ° C., and the rubber strength at the time of melting is measured at 60 ° C.
2. Sheet uniformity: According to visual evaluation.
3. Restoration rate: A strip-shaped sheet of 10 cm × 1 cm × 2 mm is immersed in a hot water bath at 80 ° C., stretched to 20 cm, and once cooled and solidified. It is immersed again in a hot water bath at 80 ° C. and contracted, and the restoration rate is calculated.
4). Sheet transparency: A sheet having a thickness of 2 mm was visually evaluated. ○: completely transparent, Δ: slightly cloudy, ×: cloudy like ground glass.

[Examples 1 and 2]
A polytransisoprene resin sheet (30 cm × 20 cm × 3 mm) obtained on the market was finely cut. This was remade into a 20 cm × 20 cm × 2 mm sheet by press molding.

  Separately, trimethylolpropane ethylene oxide-added triacrylate (Daicel-UCB TMPEOTA) was added at a ratio of 1 part by weight with respect to 100 parts by weight of the resin, and 2 ° C. at 120 ° C. using a Toyo Seiki Lab Plast Mill mixer. A 20 cm × 20 cm × 2 mm sheet was produced by press molding using a mixed resin melt-kneaded for a minute.

  These sheets were subjected to electron beam (EB) irradiation on both surfaces of the sheet under the conditions of an acceleration voltage of 200 kV and an absorbed dose of 5 Mrad. These sheets were subjected to a tensile test at 23 ° C. and 60 ° C., and the uniformity and the compound ratio of the sheets were evaluated. The results are shown in Table-1.

[Comparative Example 1]
For comparison, the same evaluation as in Example 1 was performed for the same polytransisoprene-based resin sheet (20 cm × 20 cm × 2 mm) that was not subjected to electron beam (EB) irradiation as in Example 1. The results are shown in Table-1.

[Examples 3 to 11 and Comparative Examples 2 and 3]
A sheet was prepared in the same manner as in Example 1 using tris (acryloxyethyl) isocyanurate (TAEIC) as the resin and the polyfunctional acrylic monomer shown in Table-2. The obtained sheet was irradiated with an electron beam at an acceleration voltage of 5,000 kV. Comparative Examples 2 and 3 were not irradiated with an electron beam. The obtained sheet was measured for sheet uniformity, sheet transparency, restoration rate, and strength at 500% elongation at 75 ° C., and the results are shown in Table 2.

Claims (5)

  A crosslinked polymer obtained by irradiating an active energy ray to a polytransisoprene resin or ethylene copolymer resin having a melting point of 40 to 80 ° C. to cause a crosslinking reaction.   The polytransisoprene resin or ethylene copolymer resin is a resin in which 0.1 to 30 parts by weight of a polyfunctional acrylic monomer or polyfunctional allyl monomer is mixed with 100 parts by weight of the resin constituting the polytransisoprene resin or ethylene copolymer resin. The crosslinked polymer according to claim 1.   A radiation treatment sheet comprising the crosslinked polymer according to claim 1.   A cast sheet comprising the crosslinked polymer according to claim 1 or 2.   A wig or dental mold sheet comprising the crosslinked polymer according to claim 1 or 2.