JP2011021163A - Method for producing hot melt pressure-sensitive adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a hot melt adhesive by which a solventless hot melt pressure-sensitive adhesive excellent in heat resistance and adhesion properties can be produced. <P>SOLUTION: The method for producing the hot melt pressure-sensitive adhesive comprises a coating process of coating a polymer composition on a substrate by heating and melting the same, wherein the polymer composition comprises 100 pts.wt. polymer having ≤20,000 number average molecular weight Mn and ≥6 polydispersity (weight average molecular weight Mw/number average molecular weight Mn) and 0.1-2 pts.wt. photoinitiator, and a crosslinking process of crosslinking the polymer by irradiating an active energy ray to the polymer composition having been coated on the substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a hot melt pressure-sensitive adhesive.

  Conventionally, hot melt pressure-sensitive adhesives that have been crosslinked using active energy rays have been proposed. Patent Document 1 discloses a hot melt type ultraviolet ray containing 0.01 to 1.0% by weight of at least a hydrogen abstraction type photo radical initiator as a photo radical initiator with respect to a (meth) acrylic acid ester polymer. Cross-linked transparent adhesives have been proposed.

  However, although the pressure-sensitive adhesive described in Patent Document 1 describes a suitable melt viscosity, the molecular weight of the polymer is not taken into consideration, and the hot-melt type UV-crosslinked transparent pressure-sensitive adhesive is suitable for hot-melt coating. It is not suitable.

JP 2004-262957 A

  The present invention provides a method for producing a hot-melt pressure-sensitive adhesive that can efficiently produce a solventless hot-melt pressure-sensitive adhesive having excellent heat resistance and adhesiveness.

  The method for producing a hot-melt pressure-sensitive adhesive of the present invention comprises 100 parts by weight of a polymer having a number average molecular weight Mn of 20,000 or less and a polydispersity (weight average molecular weight Mw / number average molecular weight Mn) of 6 or more. A coating step of heating and melting a polymer composition containing 0.1 to 2 parts by weight of a polymerization initiator and coating it on a substrate, and an active energy applied to the polymer composition coated on the substrate And a crosslinking step of crosslinking the polymer by irradiating a line.

  The polymer used in the coating process has a number average molecular weight Mn of 20,000 or less and a polydispersity (weight average molecular weight Mw / number average molecular weight Mn) of 6 or more. If the number average molecular weight Mn of the polymer is large, the melt viscosity of the polymer becomes large and the coating property on the substrate is lowered, so it is limited to 20,000 or less, preferably 10,000 to 20,000, 20,000 to 17,000 is more preferable.

  By limiting the polydispersity (weight average molecular weight Mw / number average molecular weight Mn) of the polymer to 6 or more, the polymer is composed of a high molecular weight component that develops adhesive force and a low molecular weight component that reduces melt viscosity. Even though the melt viscosity is low, a sufficient degree of cross-linking can be obtained, and a hot melt pressure-sensitive adhesive having excellent adhesive strength and cohesive strength can be obtained.

  On the other hand, if the polydispersity (weight average molecular weight Mw / number average molecular weight Mn) of the polymer is too large, the amount of the high molecular weight component in the polymer increases and it is difficult to apply the polymer composition onto the substrate. 20 or less is preferable, and 15 or less is more preferable.

  The number average molecular weight Mn and the weight average molecular weight Mw of the polymer were analyzed by gel permeation chromatography (GPC) using a tetrahydrofuran (THF) solution of the polymer, respectively, and the number average molecular weight Mn and the weight average molecular weight converted to polystyrene. Mw.

  The polymer is not particularly limited as long as the number average molecular weight Mn and the polydispersity are within the above-mentioned ranges, but the polymer produced by a polymerization process for polymerizing a monomer containing a (meth) acrylic acid alkyl ester is used. A polymer is preferable, and a polymer produced by a polymerization process including the following first to third processes is more preferable.

  Next, the polymerization step including the first to third steps will be described in detail. The first polymerization step comprises 100 parts by weight of a first monomer containing 60% by weight or more of a (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms, and a monomer used in the entire polymerization step. A first reactive composition containing less than 0.1 mole of iniferter with respect to a total amount of 100 moles is heated to 80 ° C. or higher and irradiated with active energy rays to give a polymerization conversion rate of 50 for the first reactive composition. The first reactive composition is polymerized so as to be ˜85% by weight. In addition, the solvent is not contained at all in the 1st reactive composition and the 2nd reactive composition and 3rd reactive composition mentioned later.

  Examples of the solvent include organic solvents used for diluting the monomer in the polymerization. For example, alcohols such as n-propanol, isopropanol, n-butanol, t-butyl alcohol, and isobutyl alcohol, ethylene Glycol monobutyl ether, methyl carbitol, ethylene glycol monobutyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, ether alcohols such as propylene glycol monomethyl ether, aromatics such as xylene and toluene, acetone , Ketones such as methyl ethyl ketone, 2-pentanone, 2-hexanone, methyl isobutyl ketone, isophorone, cyclohexanone, methyl acetate, ethyl acetate, pentyl acetate, 3-methoxybutyl acetate 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, methyl propionate, and the like esters such as ethyl propionate.

  The (meth) acrylic acid alkyl ester having 4 or more carbon atoms in the alkyl group contained in the first monomer is not particularly limited. For example, n-butyl (meth) acrylate, (meth) acrylic I-butyl acid, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, (meth) acrylic N-octyl acid, lauryl (meth) acrylate, i-nonyl (meth) acrylate, and the like. From the viewpoint of versatility and adhesive properties of the resulting polymer, n-butyl acrylate and 2-ethylhexyl acrylate are used. It is preferable to contain. In addition, the (meth) acrylic-acid alkylester whose carbon number of an alkyl group is 4 or more may be used independently, or 2 or more types may be used together. In the present invention, (meth) acrylic acid means acrylic acid or methacrylic acid.

  When the content of the alkyl group (meth) acrylic acid alkyl ester having 4 or more carbon atoms in the first monomer is small, the glass transition temperature of the polymer is high considering the use of the hot melt adhesive. Since it may become too much and the fall of adhesive force may be produced, 60 weight% or more is preferable and 65 to 97 weight% is more preferable.

  In the first monomer, if the alkyl group (meth) acrylic acid alkyl ester having 4 or more carbon atoms in the alkyl group is 60% by weight or more, the physical properties of the obtained hot melt pressure-sensitive adhesive are not impaired. In (meth) acrylic acid, alkyl group (meth) acrylic acid alkyl ester having 3 or less carbon atoms, hydroxyl group-containing (meth) acrylic acid derivative, amino group-containing (meth) acrylic acid derivative, aromatic ring-containing A (meth) acrylic acid derivative or the like may be contained.

  The (meth) acrylic acid alkyl ester having 3 or less carbon atoms in the alkyl group is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, Examples include (meth) acrylic acid alkyl esters having an alkyl group such as i-propyl (meth) acrylate having 3 or less carbon atoms, and methyl methacrylate is preferred.

  The content of (meth) acrylic acid in the first monomer is preferably 0 to 10% by weight. This is because if the content of (meth) acrylic acid is high, the adhesive strength of the resulting hot melt adhesive may be reduced or the water resistance may be reduced.

  An iniferter is contained in the first reactive composition. This iniferter is a radical initiator having a polymerization termination function by radical chain transfer, and is capable of chain transfer with an active radical having polymerization initiation ability by receiving active energy such as ultraviolet rays. After the transfer, it generates a relatively stable radical that can be dissociated again.

  The iniferter is not particularly limited. For example, N, N, N ′, N′-tetraethylthiuram disulfide, N, N, N ′, N′-tetramethylthiuram disulfide, N, N′-diethyl-N, N′-bis (2-hydroxyethyl) thiuram disulfide, N, N′-bis (N- (2-phthalimidoethyl) piperazine thiuram disulfide, N, N-dimethylthiuram disulfide, N, N′-diethylthiuram disulfide, benzyl N, N-diethyldithiocarbamate, p-xylenebis (N, N-diethyldithiocarbamate), p-xylenebis (N, N-dimethyldithiocarbamate), n-butyl-N, N-dimethyldithiocarbamate, benzyldithio Carbamate, benzyl-N, N-dimethyldithiocarbamate, etc. Are, N, N, N ', N'-tetra ethyl disulfide are preferable. Incidentally, iniferter may be also alone, or two or more are used alone.

  If the content of the iniferter in the first reactive composition is large, the polymerization rate of the first monomer may decrease. Therefore, the content of the iniferter is 0 with respect to 100 mol of the total amount of monomers used in the polymerization step. Less than 1 mol is preferable, and if the amount is too small, the glass transition temperature and the weight average molecular weight of the resulting hot-melt pressure-sensitive adhesive may increase and the adhesiveness may decrease, so the total amount of monomers used in the polymerization step is 100 mol. 0.005-0.06 mol is more preferable with respect to.

  Here, in the present invention, the “total amount of monomers used in the polymerization step” refers to the total amount of monomers present in the reaction system in the entire process of the polymerization step, specifically, the first reaction. The carbon number of the alkyl group added to the 1st monomer in an active composition, the (meth) acrylic acid ester added to the 1st reactive composition mentioned later, and the 2nd reactive composition mentioned later is The total amount of (meth) acrylic acid alkyl ester of 4 or more and other monomers added as necessary.

  The first step of the polymerization step includes a first monomer containing 60% by weight or more of a (meth) acrylic acid alkyl ester having an alkyl group with 4 or more carbon atoms and an iniferter each containing a predetermined amount. The reactive composition is preferably heated to 80 ° C. or higher, more preferably 90 to 140 ° C. and irradiated with active energy rays so that the polymerization conversion of the first reactive composition is 50 to 85% by weight. Polymerize.

  That is, while heating the first reactive composition to 80 ° C. or higher, the first reactive composition is irradiated with active energy rays to decompose the iniferter and polymerize the first reactive composition. Examples of active energy rays include ultraviolet rays, electron beams, α rays, β rays, and γ rays.

  The temperature at which the first reactive composition is polymerized is preferably 80 ° C. or higher because if the temperature is low, the reactivity of the first reactive composition may decrease and the polymerization time may become longer. In some cases, the polymerization reaction of the first reactive composition may proceed abruptly, and control of the reaction of the first reactive composition may be difficult, so 80 to 140 ° C. is more preferable.

  In the first step, the first reactive composition is polymerized until the polymerization conversion becomes 50 to 85% by weight. This is because, when the polymerization conversion rate of the first reactive composition in the first step is low, the production efficiency of the hot melt pressure-sensitive adhesive decreases, and when the polymerization conversion rate of the first reactive composition is high, This is because the viscosity of the one reactive composition increases so much that the (meth) acrylic acid ester cannot be uniformly mixed in the first reactive composition after polymerization. The polymerization conversion rate of the first reactive composition at the end of the first step is the total weight of the polymer produced at the end of the first step used for polymerization in the first reactive composition. It is a value obtained by multiplying 100 by the value obtained by dividing the total weight of the total weight of the monomer and the total weight of the unreacted monomer.

  Next, a predetermined amount of (meth) acrylic acid ester is added to the first reactive composition after completion of the polymerization in the first step to obtain a second reactive composition. It does not specifically limit as (meth) acrylic acid ester, For example, (meth) acrylic-acid 2-hydroxyethyl, (meth) acrylic-acid 2-hydroxypropyl, (meth) acrylic-acid 2-hydroxybutyl, (meth) acrylic Dimethylaminoethyl acid, diethylaminoethyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, isoamyl (meth) acrylate, benzyl (meth) acrylate, Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, N-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) Examples include isobornyl acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, i-nonyl (meth) acrylate, and the like. (Meth) acrylic acid ester may be used independently, or 2 or more types may be used together. In addition, you may add monomers, such as (meth) acrylic acid other than (meth) acrylic acid ester, to the 1st reactive composition in the range which does not impair the physical property of the polymer obtained.

  If the amount of the (meth) acrylic ester added to the first reactive composition is small, the functionalization at the molecular terminals and the adjustment of the crosslinking characteristics may be insufficient. Since the time required for polymerization of the acid ester may become long, 0.1 to 10 parts by weight is preferable with respect to 100 parts by weight of the first monomer, and 1 to 8 parts by weight is preferable.

  After that, while heating and holding the second reactive composition at 80 ° C. or higher, the second reactive composition is irradiated with active energy rays to decompose the iniferter and polymerize the second reactive composition. In addition, since it is the same as that of the above as an active energy ray, description is abbreviate | omitted.

  When the temperature at the time of polymerizing the second reactive composition is low, the progress of the reaction of the second reactive composition may be slow. Since the amount of volatilization increases and the amount of monomer remaining in the reaction system may decrease, 90 to 140 ° C. is more preferable.

  In the second step, the second reactive composition is polymerized so as to be higher than the polymerization conversion rate of the first reactive composition and 85% by weight or less. In the second step, if the polymerization conversion rate of the second reactive composition is low, the amount of the low molecular weight polymer is excessive, and if the polymerization conversion rate of the second reactive composition is high, This is because the (meth) acrylic acid alkyl ester cannot be uniformly mixed with the second reactive composition.

  The polymerization conversion rate of the second reactive composition at the end of the second step is the total weight of the polymer produced at the end of the second step, used for the polymerization at the end of the second step. A value obtained by multiplying the value obtained by dividing the total weight of the total weight of the monomer and the total weight of the unreacted monomer by 100.

  Next, a predetermined amount of (meth) acrylic acid alkyl ester having 4 or more carbon atoms in the alkyl group and an iniferter is added to the second reactive composition after the polymerization in the second step is completed. A trireactive composition is used. The (meth) acrylic acid alkyl ester and iniferter in which the alkyl group has 4 or more carbon atoms are the same as described above, and the description thereof is omitted.

  If the amount of the alkyl group (meth) acrylic acid alkyl ester having 4 or more carbon atoms added to the second reactive composition is small, the adhesiveness of the hot-melt pressure-sensitive adhesive may decrease, and is large. Then, the polymerization time in the third step may be long, so 10 to 200 parts by weight is preferable with respect to 100 parts by weight of the first monomer, and 50 to 100 parts by weight is preferable.

  If the content of the iniferter added to the second reactive composition is small, the resulting polymer may become too high in molecular weight and a gel-like product may be generated. Since the polymerization time may be slowed for a long time, 0.05 to 1 mol is preferable and 0.06 to 0.1 mol is preferable with respect to 100 mol of the total amount of monomers used in the polymerization step.

  Next, a thermal polymerization initiator is added to the third reactive composition. The thermal polymerization initiator refers to a compound that initiates radical polymerization of a monomer by generating radicals by heating. Examples of such thermal polymerization initiators include azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide, 4,4-oxybis (benzenesulfonyl hydrazide), and the like. In addition, a thermal polymerization initiator may be used independently or 2 or more types may be used together.

  If the amount of the thermal polymerization initiator added to the third reactive composition is small, the amount of residual monomer may increase, and if it is large, the amount of heat generation and gas generation due to the decomposition reaction of the thermal polymerization initiator increases. Since removal may take time and effort, it is preferably 0.1 to 2 parts by weight, more preferably 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the third reactive composition.

  Then, the third reactive composition is heated to radically polymerize the third reactive composition, and the third reactive composition is polymerized until the polymerization conversion rate of the third reactive composition reaches 98% by weight or more. To produce a polymer.

  If the temperature at which the third reactive composition is radically polymerized is low, the progress of the polymerization reaction may be slow, and if it is high, the amount of volatilization of the monomer increases and the monomer stays in the reaction system. Since the amount may decrease, 60 to 140 ° C is preferable, and 80 to 120 ° C is more preferable.

  In the third step, the third reactive composition is polymerized until the polymerization conversion rate is 98% by weight or more, preferably 98.5 to 99.8% by weight to obtain a polymer. When the polymerization conversion rate of the second reactive composition is less than 98% by weight, it takes a long time to remove the residual monomer in the hot melt pressure-sensitive adhesive. Polymerize until This is because, in the third step, when the polymerization conversion rate of the third reactive composition is low, the time required for removing the residual monomer in the hot melt pressure-sensitive adhesive becomes long.

  The polymerization conversion rate of the third reactive composition at the end of the third step is the total weight of the polymer produced at the end of the third step, which was used for the polymerization at the end of the third step. A value obtained by multiplying the value obtained by dividing the total weight of the total weight of the monomer and the total weight of the unreacted monomer by 100.

  As described above, a polymer suitable for a hot-melt pressure-sensitive adhesive is obtained within a short time of 8 hours or less by producing a polymer through a polymerization process including three steps of the first step to the third step. Can do.

  Next, a photopolymerization initiator different from the iniferter is added to the polymer to produce a polymer composition. In adding the photopolymerization initiator to the polymer, since the photopolymerization initiator can be uniformly mixed with the polymer, the polymer is heated to 100 to 200 ° C. to be in a molten state. It is preferable to add a photopolymerization initiator to the coalescence.

  The photopolymerization initiator different from the above iniferter is not particularly limited as long as it generates radicals by light irradiation. For example, α-hydroxyketone compound, acetophenone compound, benzophenone compound, benzoin compound, benzoin ether Compounds, benzyl ketal compounds, acyl phosphine oxide compounds, thioxanthone compounds, diacetyl and derivatives thereof, anthraquinones and derivatives thereof, diphenyl disulfides and derivatives thereof, organic disulfides such as tetramethylthiuram disulfide and dibenzoyl disulfide, etc. ) 2,2-dimethoxy-1,2-diphenylethane-1-one is preferable from the viewpoint of reactivity with acrylic acid alkyl ester and (meth) acrylic acid. In addition, a photoinitiator may be used independently or 2 or more types may be used together.

  When the amount of the photopolymerization initiator added to the polymer obtained in the polymerization step is small, the crosslinking rate when the polymer is crosslinked after coating the polymer on the substrate as described later is lowered. However, at most, the effect of adding the photopolymerization initiator is not changed, and the possibility that an unreacted photopolymerization initiator remains is high. Therefore, with respect to 100 parts by weight of the polymer obtained in the polymerization step, Is limited to 0.1 to 2 parts by weight, preferably 0.8 to 2 parts by weight, and more preferably 1 to 1.8 parts by weight.

  In addition to the photopolymerization initiator, a radical reactive crosslinking agent, a tackifier, a plasticizer, a filler, a pigment, and the like may be added to the polymer obtained in the polymerization step.

  The radical reactive crosslinking agent is not particularly limited, and examples thereof include ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, allyl methacrylate, vinyl methacrylate, glycerol dimethacrylate, triallyl isocyanurate, divinyl adipate, di Vinyl ether, divinylbenzene, diallylamine, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,4 butanediol dimethacrylate, trimethylolpropane trimethacrylate, glycerol dimethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, triethylene glycol di Methacrylate, 1,3-butanediol dimethacrylate Triethylene glycol diacrylate, dimethylol-tricyclodecane diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, trimethylolpropane acrylic acid benzoate, 2-hydroxy-3-acryloyloxypropyl methacrylate, dipentaerythritol hexa Acrylate, dipentaerythritol hexamethacrylate, polyethylene glycol diacrylate having a number average molecular weight of 200, polyethylene glycol diacrylate having a number average molecular weight of 400, polyethylene glycol diacrylate having a number average molecular weight of 600, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, dimethyl Roll-tricyclodecane diacrylate, ethylene oxide-modified trimethylolpropane triacrylate, polyethylene glycol dimethacrylate having a number average molecular weight of 200, polyethylene glycol dimethacrylate having a number average molecular weight of 400, polyethylene glycol dimethacrylate having a number average molecular weight of 600 Examples include monomers having two or more polymerizable unsaturated bonds in one molecule such as methacrylate, and ethylene glycol dimethacrylate is preferred.

  If the amount of the radical reactive crosslinking agent added to the polymer is small, the effect of adding the radical reactive crosslinking agent may not be exhibited, and at most, the effect of improving the degree of crosslinking of the polymer is not changed. Since the amount of the remaining radical-reactive cross-linking agent may increase, 0.1 to 10 parts by weight is preferable with respect to 100 parts by weight of the polymer, and 0.5 to 5 parts by weight is more preferable.

  Next, the polymer composition is heated and melted, and coated on the base material in a general-purpose manner so that the thickness is preferably constant (coating step). In addition, it does not specifically limit as a base material, For example, a polyethylene terephthalate film, a polyvinyl chloride film, paper, a nonwoven fabric etc. are mentioned.

  Thereafter, the hot melt pressure-sensitive adhesive can be obtained by irradiating the polymer composition coated on the substrate with active energy rays to crosslink the polymer. In addition, since an active energy ray is the same as the above-mentioned, description is abbreviate | omitted.

  When the melt viscosity at 110 ° C. of the polymer composition is high, it may be difficult to apply the polymer composition to a predetermined thickness on the base material. Therefore, it is preferably 14 Pa · s or less, and 8 to 13 Pa. -S is more preferable. The melt viscosity at 110 ° C. of the polymer composition refers to that measured according to JIS K6862.

  When the gel fraction of the obtained hot-melt pressure-sensitive adhesive is low, the hot-melt pressure-sensitive adhesive may remain on the adherend when it is peeled off. Therefore, 45% by weight or more is preferable, and 50 to 98% by weight is preferable.

In addition, the gel fraction of a hot melt adhesive means what was measured in the following way. The hot melt adhesive was weighed, the hot melt adhesive was immersed in ethyl acetate at 23 ° C. for 24 hours, the insoluble matter was filtered through a 200 mesh wire mesh, and the residue on the wire mesh was vacuum dried to remove the dry residue. The weight is measured (Bg) and calculated by the following formula.
Gel fraction (% by weight) = (B / A) × 100

  Since the manufacturing method of the hot-melt pressure-sensitive adhesive of the present invention is as described above, a hot-melt pressure-sensitive adhesive having excellent heat resistance and cohesion can be easily manufactured.

  And a pressure-sensitive adhesive suitable for hot-melt coating can be easily produced in a short time by producing the polymer through the above-mentioned three polymerization steps from the first step to the third step.

Example 1
A first monomer comprising 5 g (0.050 mol) of methyl methacrylate, 33 g (0.26 mol) of butyl acrylate and 62 g (0.34 mol) of 2-ethylhexyl acrylate, and N, N, N ′ , N′-tetraethylthiuram disulfide 0.11 g (0.00037 mol) is fed to a 3 liter heat-resistant glass reaction flask equipped with a condenser, stirring blade, thermometer and heater. The atmosphere in the reaction flask was a nitrogen gas atmosphere.

  Next, with the first reactive composition heated and held at 90 ° C., the first reactive composition was polymerized for 2 hours by irradiating the first reactive composition with ultraviolet rays using a 9 W ultraviolet lamp, and the first reaction The polymerizable composition was polymerized until the polymerization conversion reached 65% by weight (first step).

  Subsequently, while maintaining the first reactive composition that has completed the first step at 90 ° C., 5 g (0.043 mol) of 2-hydroxyethyl acrylate is added to the first reactive composition at a time and uniformly. A second reactive composition was obtained by mixing.

  Then, while heating and holding the second reactive composition at 90 ° C., the second reactive composition was polymerized for 1 hour by irradiating with ultraviolet rays using a 9 W ultraviolet lamp. The composition was polymerized until the polymerization conversion reached 85% by weight (second step).

  On the other hand, a mixed solution was prepared by uniformly mixing 62 g (0.336 mol) of 2-ethylhexyl acrylate and 0.23 g (0.0008 mol) of N, N, N ′, N′-tetraethylthiuram disulfide. Then, while heating and maintaining the second reactive composition that has completed the second step in the reaction flask at 90 ° C., the above mixed solution is added to the second reactive composition at once and mixed uniformly. A third reactive composition was prepared. In addition, the polymer manufactured in the first step and the second step was dissolved in 2-ethylhexyl acrylate.

  Next, 1.6 g of azobisisobutyronitrile was added to the third reactive composition, and then the third reactive composition was heated to 100 ° C. so that the polymerization conversion of the third reactive composition was 99. Acrylic copolymer was obtained by polymerization until the weight percentage was reached (third step).

  The resulting acrylic copolymer had a number average molecular weight Mn of 17,000, a weight average molecular weight Mw of 21.25, and a polydispersity of 12.5.

  After 100 g of acrylic copolymer was heated to 120 ° C. and melted, 1 g of 2,2-dimethoxy-1,2-diphenylethane-1-one was added to 100 g of acrylic copolymer and mixed uniformly. Thus, a polymer composition was produced. The melt viscosity at 110 ° C. of the polymer composition was 13 Pa · s.

  The polymer composition was applied to a thickness of 15 μm on one surface of a polyethylene terephthalate film having a thickness of 38 μm.

The polymer composition was irradiated with ultraviolet rays continuously for 2 minutes at an irradiation intensity of ² mW / cm ² using an ultraviolet lamp to crosslink the acrylic copolymer to obtain a hot melt adhesive. . The gel fraction of the obtained hot melt pressure-sensitive adhesive was 60% by weight.

  In the first step, N, N, N ′, N′-tetraethylthiuram disulfide contained in the first reactive composition is added to 100 mol of all monomers used in the first to third steps. The amount was 0.036 mol. In the third step, the N, N, N ′, N′-tetraethylthiuram disulfide contained in the third reactive composition is based on 100 mol of all monomers used in the first to third steps. It was 0.081 mol.

(Example 2)
In the second step, the same procedure as in Example 1 was conducted except that 8 g (0.045 mol) of benzyl methacrylate was added to the first reactive composition instead of 5 g (0.043 mol) of 2-hydroxyethyl acrylate. To obtain a hot melt adhesive.

  The resulting acrylic copolymer had a number average molecular weight Mn of 13,000, a weight average molecular weight Mw of 14.04, and a polydispersity of 10.8. The melt viscosity at 110 ° C. of the polymer composition was 10.5 Pa · s. The gel fraction of the obtained hot melt adhesive was 55% by weight.

  In the first step, N, N, N ′, N′-tetraethylthiuram disulfide contained in the first reactive composition is added to 100 mol of all monomers used in the first to third steps. The amount was 0.0036 mol. In the third step, the N, N, N ′, N′-tetraethylthiuram disulfide contained in the third reactive composition is based on 100 mol of all monomers used in the first to third steps. It was 0.081 mol.

(Comparative Example 1)
From a monomer consisting of 5 g (0.050 mol) of methyl methacrylate, 33 g (0.26 mol) of butyl acrylate and 129 g (0.70 mol) of 2-ethylhexyl acrylate, and 1.7 g of azobisisobutyronitrile The monomer composition to be dissolved in 300 g of ethyl acetate was supplied to a 3 liter heat-resistant glass reaction flask equipped with a condenser, a stirring blade, a thermometer and a heater, and the reaction flask was filled with a nitrogen gas atmosphere. .

  Next, after the monomer composition is heated and held at 90 ° C. and polymerized for 6 hours, the reaction solution in the reaction flask is heated to 120 ° C. and vacuum degassed for 24 hours. Ethyl acetate was removed to obtain an acrylic copolymer.

(Comparative Example 2)
It consists of 5 g (0.050 mol) of methyl methacrylate, 33 g (0.26 mol) of butyl acrylate, 124 g (0.67 mol) of 2-ethylhexyl acrylate and 5 g (0.043 mol) of 2-hydroxyethyl acrylate. A monomer composition composed of 4.25 g of monomer and azobisisobutyronitrile was dissolved in 300 g of ethyl acetate, and then a reaction made of 3 liters of heat-resistant glass equipped with a condenser, a stirring blade, a thermometer and a heater. The reaction flask was fed to a nitrogen gas atmosphere.

  Next, after the monomer composition is heated and held at 90 ° C. and polymerized for 4 hours, the reaction solution in the reaction flask is heated to 120 ° C. and vacuum degassed for 24 hours. Ethyl acetate was removed to obtain an acrylic copolymer.

Claims (3)

100 parts by weight of a polymer having a number average molecular weight Mn of 20,000 or less and a polydispersity (weight average molecular weight Mw / number average molecular weight Mn) of 6 or more and 0.1 to 2 parts by weight of a photopolymerization initiator A coating step of heating and melting the polymer composition to be coated on the substrate, and crosslinking for irradiating the polymer composition coated on the substrate with active energy rays to crosslink the polymer A process for producing a hot melt pressure-sensitive adhesive. The method for producing a hot melt pressure-sensitive adhesive according to claim 1, wherein the polymer is obtained by polymerizing a monomer containing a (meth) acrylic acid alkyl ester. The polymer is obtained by a polymerization step of polymerizing a monomer containing a (meth) acrylic acid alkyl ester, and the polymerization step is a step of converting a (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms to 60. A first reactive composition containing 100 parts by weight of a first monomer containing at least wt% and less than 0.1 mol of iniferter with respect to 100 mol of the total amount of monomers used in the polymerization step is 80 ° C. The first step of polymerizing the first reactive composition so that the polymerization conversion rate of the first reactive composition is 50 to 85% by weight by heating and irradiating with active energy rays, and the first reaction 0.1 to 10 parts by weight of (meth) acrylic acid ester to 100 parts by weight of the first monomer is added to the reactive composition to form a second reactive composition. Heat and hold above 80 ° C The second reactive composition is irradiated with active energy rays so that the polymerization conversion of the second reactive composition is higher than the polymerization conversion of the first reactive composition and not more than 85% by weight. And (meth) acrylic acid alkyl ester having 4 or more carbon atoms in the alkyl group in 10% by weight of the first monomer. 200 parts by weight and 0.05 to 1 mol of iniferter are added to 100 mol of the total amount of monomers used in the polymerization step to form a third reactive composition, and this third reactive composition is heated. A polymerization initiator is added in an amount of 0.1 to 2 parts by weight with respect to 100 parts by weight of the third reactive composition, and the third reactive composition is polymerized so that the polymerization conversion is 98% by weight or more. And a third step of producing a polymer. Method for producing a hot melt adhesive of claim 1, wherein the.