JP4279153B2 - Release paper base paper - Google Patents

Description

  The present invention relates to a release paper base paper. More specifically, a release paper having a specific molecular weight distribution and having a coating layer made of a vinyl alcohol polymer containing a silyl group on at least one surface of the release paper substrate and excellent in barrier properties and water resistance. Regarding the base paper.

  The release paper is coated with an oily varnish containing a water- and oil-repellent silicone resin and a solvent (such as toluene) on the paper to give the surface release properties. Adhesive labels, adhesive tapes, industrial It is used as a base material for obtaining adhesive paper and as release paper. However, paper has many voids between pulp fibers, which are the main constituents of the paper, and has high permeability and air permeability. Therefore, when the varnish is applied directly to the paper surface, the varnish is contained in the paper. In addition to being able to obtain a release paper having sufficient release performance, it is uneconomical.

  For the above problem, a method of coating an aqueous PVA solution on the paper surface using the excellent film forming ability and oil resistance of polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) is generally used. Yes. Of these, partially saponified PVA is preferred because of its excellent barrier properties. However, although partially saponified PVA has excellent barrier properties against oil varnishes and solvents contained therein, it is inferior in water resistance, and there is a problem that polyvinyl alcohol is eluted and blocked by humidification in an adhesive processing step or the like. Furthermore, there is a problem that the water dispersible varnish cannot be used in the post-processing step. For example, when used as a sealing agent for release paper base paper, the water resistance to emulsion type silicone used as a release agent, and the water resistance to emulsion type adhesive in the subsequent adhesive processing step are insufficient. There was a problem.

  In Japanese Patent Application Laid-Open No. 58-214596 (Patent Document 1), modified polyvinyl alcohol (silyl group-containing PVA) which is a saponified product of a copolymer of a vinyl ester and an unsaturated monomer containing silicon in the molecule is disclosed. A method for producing processed paper base paper, characterized in that the base paper is coated is described. The processed paper base paper produced here is suitably used as a base paper for release paper to be processed with silicone, and is superior in permeation preventing effect to organic solvents or release agents, that is, barrier properties, compared to unmodified PVA. Has been.

  However, in general, silyl group-containing PVA sometimes cannot be dissolved in water unless an alkali or acid such as sodium hydroxide is added when preparing an aqueous solution for application to paper. Moreover, the viscosity stability of the aqueous solution of silyl group-containing PVA is insufficient, and the viscosity of the aqueous solution used for coating may fluctuate. Moreover, the water resistance of the coating film obtained from the aqueous solution of the silyl group-containing PVA is not sufficient, and as a result, the calendar may be soiled during the calendar process, which has been an obstacle to production with high productivity. . Furthermore, since the barrier property of the obtained coating film against the organic solvent is insufficient, the coating liquid containing the organic solvent applied for processing is easily absorbed in the paper, and the yield on the surface is reduced. There was also a problem of doing.

JP 58-214596 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a release paper base having excellent coating properties and excellent barrier properties against water and water resistance.

（Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、ｍは０〜２の整数である。）
で示されるシリル基を有する単量体単位を含有するビニルエステル系重合体をけん化することによって得られるビニルアルコール系重合体であって、下記式（Ｉ）及び式（II）を満足し、けん化度が９５モル％以上であり、その４％水溶液のｐＨが４〜８であり、かつビニルアルコール系重合体の中で、その重合度が重量平均重合度の３倍を超える重合体の重量分率が２５重量％以下であるとともに、その重合度が重量平均重合度の１／２倍よりも小さい重合体の重量分率が１２重量％以下であることを特徴とするビニルアルコール系重合体からなる塗工層を、剥離紙基材の少なくとも１面に有する剥離紙原紙を提供することによって達成される。
２０＜Ｐｗ×Ｓ＜４６０ ・・・（Ｉ）
Ｐｗ：ビニルアルコール系重合体の重量平均重合度
Ｓ：一般式（１）で示されるシリル基を有する単量体単位の含有量（モル％）
０．１／１００≦（Ａ−Ｂ）／（Ｂ）≦５０／１００ ・・・（II）
Ａ：ビニルアルコール系重合体中のケイ素原子の含有量（単位：ｐｐｍ）
Ｂ：水酸化ナトリウムを含有するメタノールで洗浄し、次いでメタノールによるソックスレー抽出により洗浄したビニルアルコール系重合体中のケイ素原子の含有量（単位：ｐｐｍ）
ここで、ＡおよびＢは、それぞれ測定試料を灰化した後、ＩＣＰ発光分析法により測定される。
The above problem is solved by the following general formula (1)

(R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have an oxygen-containing substituent, and m is 0 to 2 Is an integer.)
A vinyl alcohol polymer obtained by saponifying a vinyl ester polymer containing a monomer unit having a silyl group represented by the formula , satisfying the following formulas (I) and (II) , and saponifying The weight fraction of the polymer having a degree of 95% by mole or more, a pH of the 4% aqueous solution of 4 to 8, and a degree of polymerization exceeding 3 times the weight average degree of polymerization in the vinyl alcohol polymer. A vinyl alcohol polymer characterized in that the weight fraction of a polymer having a rate of 25% by weight or less and a polymerization degree smaller than ½ times the weight average polymerization degree is 12% by weight or less This is achieved by providing a release paper base paper having a coating layer to be formed on at least one surface of the release paper substrate.
20 <Pw × S <460 (I)
Pw: Weight average polymerization degree of vinyl alcohol polymer S: Content of monomer unit having silyl group represented by general formula (1) (mol%)
0.1 / 100 ≦ (A−B) / (B) ≦ 50/100 (II)
A: Content of silicon atom in vinyl alcohol polymer (unit: ppm)
B: Content of silicon atom in vinyl alcohol polymer washed with methanol containing sodium hydroxide and then washed with Soxhlet extraction with methanol (unit: ppm)
Here, A and B are measured by ICP emission spectrometry after ashing the measurement sample.

（式中、Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、ｍは０〜２の整数であり、ｎは０〜４の整数である。）
または下記の一般式（３）

（式中、Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、Ｒ^３は水素原子またはメチル基であり、Ｒ^４は水素原子または炭素数１〜５のアルキル基であり、Ｒ^５は炭素数１〜５のアルキレン基であるか、または酸素原子もしくは窒素原子を含む２価の炭化水素基であり、ｍは０〜２の整数である。）
で示される単量体である。 In a preferred embodiment, the monomer having a silyl group is represented by the following general formula (2):

(Wherein R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have a substituent containing oxygen, and m is (It is an integer from 0 to 2, and n is an integer from 0 to 4.)
Or the following general formula (3)

(In the formula, R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have a substituent containing oxygen, and R ³ Is a hydrogen atom or a methyl group, R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁵ is an alkylene group having 1 to ⁵ carbon atoms, or 2 containing an oxygen atom or a nitrogen atom Is a valent hydrocarbon group, and m is an integer of 0 to 2.)
It is a monomer shown by.

  The release paper base paper of the present invention has an excellent barrier property against an organic solvent, and can effectively prevent the coating liquid containing the organic solvent applied for processing from being easily absorbed into the paper. it can. Moreover, the water resistance of the coating film is excellent, and as a result, the calendar is hardly stained during the calendar process, and can be manufactured with high productivity. Furthermore, the viscosity stability of the coating liquid is also excellent, and the coating liquid can be adjusted without adding an alkali or an acid.

  As described above, the vinyl alcohol polymer used in the present invention has the following general formula (1).

（Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、ｍは０〜２の整数である。）
で示されるシリル基を有する単量体単位を含有するビニルエステル系重合体をけん化することによって得られるビニルアルコール系重合体であって、下記式（Ｉ）を満足し、かつビニルアルコール系重合体の中で、その重合度が重量平均重合度の３倍を超える重合体の重量分率が２５重量％以下であることが必要である。
２０＜Ｐｗ×Ｓ＜４６０ ・・・（Ｉ）
Ｐｗ：ビニルアルコール系重合体の重量平均重合度
Ｓ：一般式（１）で示されるシリル基を有する単量体単位の含有量（モル％）

(R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have an oxygen-containing substituent, and m is 0 to 2 Is an integer.)
A vinyl alcohol polymer obtained by saponifying a vinyl ester polymer containing a monomer unit having a silyl group represented by formula (1), which satisfies the following formula (I) and is a vinyl alcohol polymer: Among these, it is necessary that the weight fraction of the polymer whose degree of polymerization exceeds 3 times the weight average degree of polymerization is 25% by weight or less.
20 <Pw × S <460 (I)
Pw: Weight average polymerization degree of vinyl alcohol polymer S: Content of monomer unit having silyl group represented by general formula (1) (mol%)

  The vinyl alcohol polymer used in the present invention has a product (Pw × S) of the weight average polymerization degree (Pw) of the vinyl alcohol polymer and the content (S) of the monomer unit having a silyl group (20 < It is necessary to satisfy the relationship of Pw × S <460. Pw × S preferably satisfies the relationship of 50 <Pw × S <420, more preferably 100 <Pw × S <390. When Pw × S is 20 or less, the film formed from the aqueous solution of silyl group-containing PVA has insufficient water resistance, and when Pw × S is 460 or more, silyl group must be added without adding alkali or the like. The contained PVA may not be dissolved in water.

  Among vinyl alcohol polymers, when the weight fraction of a polymer whose degree of polymerization exceeds 3 times the weight average degree of polymerization Pw exceeds 25% by weight, the viscosity stability of the aqueous solution of the vinyl alcohol polymer Decreases.

  Among the vinyl alcohol polymers, when the weight fraction of the polymer having a degree of polymerization exceeding 3 times the weight average degree of polymerization Pw exceeds 25% by weight, the viscosity stability of the aqueous solution of the vinyl alcohol polymer is The reason for the decrease is considered as follows.

  Among all the monomer units contained in the polymer having a silyl group, the monomer unit having a silyl group is uniformly present. Therefore, as the degree of polymerization of the polymer increases, one molecule of the polymer. The number of monomer units having a silyl group contained in is increased. And as the number of monomer units having a silyl group contained in one polymer molecule increases, the polymer is more susceptible to the influence of the silyl group. That is, a polymer having a high degree of polymerization is more susceptible to silyl groups than a polymer having a low degree of polymerization. Therefore, the vinyl alcohol polymer containing a large amount of the high polymerization degree component contains a large amount of the polymer that is easily affected by the silyl group, and therefore, it is considered that the viscosity stability of the aqueous solution is lowered.

  On the other hand, the smaller the degree of polymerization of the polymer, the smaller the number of monomer units having a silyl group contained in one molecule of the polymer. The smaller the number of monomer units having a silyl group contained in one molecule of the polymer, the less likely the polymer is affected by the silyl group. That is, the effect of the silyl group is less likely to appear in a polymer having a lower degree of polymerization than in a polymer having a higher degree of polymerization. Therefore, the vinyl alcohol polymer containing a large amount of low polymerization degree components contains a large amount of a polymer having a small silyl group effect.

  The vinyl alcohol polymer used in the present invention preferably has a weight fraction of a polymer having a degree of polymerization smaller than ½ times the weight average degree of polymerization Pw of 12% by weight or less. Among vinyl alcohol polymers, when the polymer weight fraction is less than ½ times the weight average degree of polymerization and the weight fraction of the polymer exceeds 12% by weight, the low degree of polymerization with little effect of silyl groups Since many components are contained, the water resistance and organic solvent barrier property of the film may be lowered.

  The weight average degree of polymerization (Pw) and the degree of polymerization distribution of the vinyl alcohol polymer can be determined, for example, by GPC-LALLS measurement. That is, by re-saponifying and purifying the silyl group-containing PVA to a saponification degree of 99.5 mol% or more, and then dividing the weight average molecular weight determined by GPC-LALLS by the formula weight 44 of the vinyl alcohol monomer unit. The weight average degree of polymerization is determined. Further, the weight fraction of the polymer having a polymerization degree within a specific range can be determined from the integral polymerization degree distribution obtained from GPC-LALLS measurement.

In the vinyl alcohol polymer used in the present invention, the content S (mol%) of the monomer unit having a silyl group is determined from proton NMR of the vinyl ester polymer before saponification. When the proton NMR of the vinyl ester polymer before saponification is measured here, the vinyl ester polymer is purified by reprecipitation with hexane-acetone, and a monomer having an unreacted silyl group from the polymer. Then, after drying at 90 ° C. under reduced pressure for 2 days, it is dissolved in CDCl ₃ solvent and used for analysis.

The vinyl alcohol polymer used in the present invention preferably satisfies the following formula (II).
0.1 / 100 ≦ (A−B) / (B) ≦ 50/100 (II)
A: Content of silicon atom in vinyl alcohol polymer (unit: ppm)
B: Content of silicon atom in vinyl alcohol polymer washed with methanol containing sodium hydroxide and then washed with Soxhlet extraction with methanol (unit: ppm)
Here, A and B are measured by ICP emission spectrometry after ashing the measurement sample.

  Here, in order to obtain the silicon atom content (B), a standard washing method of the vinyl alcohol polymer is a washing operation with methanol containing sodium hydroxide (1 part by weight of vinyl alcohol polymer). In contrast, 10 parts by weight of a methanol solution containing sodium hydroxide was added so that the molar ratio of sodium hydroxide to vinyl alcohol monomer units in the vinyl alcohol polymer was 0.01. The operation of boiling the mixture for 1 hour and then filtering the polymer) is repeated 5 times, followed by Soxhlet extraction with methanol for 1 week. In the above washing method, the washing operation with methanol containing sodium hydroxide and the Soxhlet extraction with methanol are performed until the silicon atom content in the vinyl alcohol polymer is almost unchanged, and this condition is satisfied. In such a range, the number of washing operations with methanol containing sodium hydroxide and the Soxhlet extraction period with methanol may be appropriately increased or decreased.

  The silicon atom content (A) of the vinyl alcohol polymer is considered to indicate the content of all silicon atoms contained in the vinyl alcohol polymer. Further, the content (B) of the silicon atom in the vinyl alcohol polymer washed with methanol containing sodium hydroxide and then washed by Soxhlet extraction with methanol is directly incorporated into the main chain of the vinyl alcohol polymer. This is considered to indicate the content of silicon atoms derived from the silyl group-containing monomer.

  In determining the silicon atom content (B), the vinyl alcohol polymer is washed with methanol containing sodium hydroxide, and at that time, the siloxane bond (—Si—O—Si—) is broken. At this time, the silyl group-containing monomer that was not directly incorporated into the main chain of the vinyl alcohol polymer and was bonded to the main chain of the vinyl alcohol polymer via a siloxane bond was obtained from the vinyl alcohol polymer. Is removed from the polymer. Therefore, the silicon atom content (B) is considered to indicate the silicon atom content in a state in which the silyl group-containing monomer not directly incorporated in the main chain of the vinyl alcohol polymer is removed. It is done. Therefore, (AB) in the above relational expression 0.1 / 100 ≦ (AB) / (B) ≦ 50/100 represents a silyl group that is not directly introduced into the main chain of the vinyl alcohol polymer. It is considered that the content of the silyl group derived from the monomer unit it has is shown.

  When the value of (AB) / (B) in the vinyl alcohol polymer is large, it means that the vinyl alcohol polymer contains many monomer units having an excess silyl group. In the case where the value of (A-B) / (B) in the vinyl alcohol polymer is small, the monomer unit having an excess silyl group that is not directly introduced into the main chain of the vinyl alcohol polymer Means less.

  A preferred range of (A-B) / (B) is 0.1 / 100 to 50/100, a more preferred range is 0.3 / 100 to 25/100, and a particularly preferred range is 0.4 / 100. ~ 20/100. When (A-B) / (B) exceeds 50/100, a siloxane bond between a monomer unit containing an excess silyl group and a silyl group-containing monomer unit incorporated in the main chain ( -Si-O-Si-) is formed in a large number, the molecular mobility of the vinyl alcohol polymer is limited, the viscosity stability of the aqueous solution of the vinyl alcohol polymer is reduced, and the organic solvent barrier is reduced. It is thought that the nature may decrease. On the other hand, when (AB) / (B) is less than 0.1 / 100, a monomer unit containing an excess silyl group and a silyl group-containing monomer unit incorporated in the main chain The ratio of siloxane groups (—Si—O—Si—) formed between the silane group and the amount of silyl groups contained in the vinyl alcohol polymer decreases, and the organic solvent barrier property is considered to decrease. It is done. Furthermore, a vinyl alcohol polymer in which (A-B) / (B) is less than 0.1 / 100 is unrealistic because it requires a high cost for cleaning during production.

  Furthermore, it is preferable that the pH of the 4% aqueous solution of the vinyl alcohol polymer used in the present invention is 4-8. The more preferable range of the pH of the 4% aqueous solution is 4.5 to 7, and the particularly preferable range is 5 to 6.5. When the pH of the 4% aqueous solution is less than 4, the viscosity stability of the vinyl alcohol polymer aqueous solution may be lowered, and the organic solvent barrier property may be lowered. On the other hand, when the pH of the 4% aqueous solution exceeds 8, the water resistance of the coating film is lowered, and calendar stains may occur during the coating operation, and the organic solvent barrier property is lowered.

In the general formula (1) representing the silyl group contained in the vinyl alcohol polymer used in the present invention, R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, These groups may have a substituent containing oxygen, and m is an integer of 0 to 2.

Here, examples of the alkyl group having 1 to 5 carbon atoms represented by R ¹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, and isobutyl. Group, n-pentyl group, tert-pentyl group, isopentyl group and the like. Examples of the alkoxyl group represented by R ² include methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, tert-butoxy group, pentoxy group, hexyloxy group, octyloxy group, lauryloxy group, and oleyloxy group. In addition, examples of the acyloxyl group include an acetoxy group and a propionyloxy group. These alkoxyl groups or acyloxyl groups may have an oxygen-containing substituent, and examples of the substituent include alkoxyl groups such as a methoxy group and an ethoxy group.

  The vinyl alcohol polymer used in the present invention is obtained by copolymerizing a vinyl ester monomer and a monomer having a silyl group represented by the general formula (1) to saponify the resulting vinyl ester polymer. Can be manufactured.

  The vinyl alcohol polymer of the present invention comprises a vinyl ester monomer and a monomer having a silyl group represented by the general formula (1), such as 2-mercaptoethanol, n-dodecyl mercaptan, mercaptoacetic acid, 3- It can also be produced by copolymerization in the presence of a thiol compound such as mercaptopropionic acid and saponifying the resulting vinyl ester polymer. By this method, a vinyl alcohol polymer in which a functional group derived from a thiol compound is introduced at the terminal is obtained.

  Examples of vinyl ester monomers used in the production of such vinyl alcohol polymers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, and benzoate. Examples thereof include vinyl acid vinyl, vinyl pivalate, and versatic acid vinyl, and vinyl acetate is particularly preferable.

  As a monomer having a silyl group represented by the general formula (1) used for radical copolymerization with a vinyl ester monomer, the following general formula (2)

（式中、Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、ｍは０〜２の整数であり、ｎは０〜４の整数である。）
または下記の一般式（３）

(Wherein R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have a substituent containing oxygen, and m is (It is an integer from 0 to 2, and n is an integer from 0 to 4.)
Or the following general formula (3)

（式中、Ｒ^１は炭素数１〜５のアルキル基であり、Ｒ^２はアルコキシル基またはアシロキシル基であって、これらの基は酸素を含有する置換基を有していてもよく、Ｒ^３は水素原子またはメチル基であり、Ｒ^４は水素原子または炭素数１〜５のアルキル基であり、Ｒ^５は炭素数１〜５のアルキレン基であるかまたは酸素原子もしくは窒素原子を含む２価の炭化水素基であり、ｍは０〜２の整数である。）
で示される化合物を挙げることができる。

(In the formula, R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have a substituent containing oxygen, and R ³ Is a hydrogen atom or a methyl group, R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁵ is an alkylene group having 1 to ⁵ carbon atoms, or a divalent atom containing an oxygen atom or a nitrogen atom And m is an integer of 0 to 2.)
The compound shown by can be mentioned.

In the general formula (2) and general formula (3), examples of the alkyl group having 1 to 5 carbon atoms represented by R ¹ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, Examples include sec-butyl group, tert-butyl group, isobutyl group, n-pentyl group, tert-pentyl group, isopentyl group and the like. Examples of the alkoxyl group represented by R ² include methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, tert-butoxy group, pentoxy group, hexyloxy group, octyloxy group, lauryloxy group, and oleyloxy group. In addition, examples of the acyloxyl group include an acetoxy group and a propionyloxy group. These alkoxyl groups or acyloxyl groups may have an oxygen-containing substituent, and examples of the substituent include alkoxyl groups such as a methoxy group and an ethoxy group. Examples of the alkyl group having 1 to 5 carbon atoms represented by R ⁴ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, and an isobutyl group. , N-pentyl group, tert-pentyl group, isopentyl group and the like. Examples of the alkylene group having 1 to 5 carbon atoms represented by R ⁵ include a methylene group, an ethylene group, a dimethylethylene group, a trimethylene group, a tetramethylene group, and a pentamethylene group, and an oxygen atom or a nitrogen atom. Examples of the divalent hydrocarbon group to be included include —CH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ —, —CH ₂ CH ₂ NHCH ₂ CH ₂ —, —CH ₂ CH ₂ NHCH ₂ —, —CH ₂ CH ₂ N ( _{CH 3) CH 2 CH 2 -} , - CH 2 CH 2 N (CH 3) CH 2 -, - CH 2 CH 2 OCH 2 CH 2 CH 2 -, - CH 2 CH 2 OCH 2 CH 2 -, - CH 2 CH ₂ OCH ₂ — and the like can be mentioned.

Examples of the monomer represented by the above formula (2) include vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, and allyltrimethoxy. Silane, allylmethyldimethoxysilane, allyldimethylmethoxysilane, allyltriethoxysilane, allylmethyldiethoxysilane, allyldimethylethoxysilane, vinyltris (β-methoxyethoxy) silane, vinylisobutyldimethoxysilane, vinylethyldimethoxysilane, vinylmethoxydi Butoxysilane, vinyldimethoxybutoxysilane, vinyltributoxysilane, vinylmethoxydihexyloxysilane, vinyldimethoxyhexyloxysilane, vinyl Rehexyloxy silane, vinyl methoxy dioctyloxy silane, vinyl dimethoxy octyloxy silane, vinyl trioctyloxy silane, vinyl methoxy dilauryl silane, vinyl dimethoxy lauryloxy silane, vinyl methoxy dioleoxy silane, vinyl dimethoxy oleyloxy silane, etc. Is mentioned.
In the above formula (2), when a monomer having a silyl group with n of 1 or more and a vinyl ester monomer are copolymerized, the degree of polymerization of the resulting vinyl ester polymer tends to decrease. In that respect, when vinyltrimethoxysilane is copolymerized with a vinyl ester monomer, it is possible to suppress a decrease in the degree of polymerization of the resulting vinyl ester polymer, and industrial production is easy and inexpensive. Since it can be obtained, it can be preferably used.

  Examples of the monomer represented by the above formula (3) include 3- (meth) acrylamide-propyltrimethoxysilane, 3- (meth) acrylamide-propyltriethoxysilane, and 3- (meth) acrylamide-propyl. Tri (β-methoxyethoxy) silane, 2- (meth) acrylamide-ethyltrimethoxysilane, 1- (meth) acrylamide-methyltrimethoxysilane, 2- (meth) acrylamide-2-methylpropyltrimethoxysilane, 2- (Meth) acrylamide-isopropyltrimethoxysilane, N- (2- (meth) acrylamide-ethyl) -aminopropyltrimethoxysilane, (3- (meth) acrylamide-propyl) -oxypropyltrimethoxysilane, 3- (meta ) Acrylamide-propyltria Toxisilane, 2- (meth) acrylamide-ethyltriacetoxysilane, 4- (meth) acrylamide-butyltriacetoxysilane, 3- (meth) acrylamide-propyltripropionyloxysilane, 2- (meth) acrylamide-2-methylpropyl Triacetoxysilane, N- (2- (meth) acrylamide-ethyl) -aminopropyltriacetoxysilane, 3- (meth) acrylamide-propylisobutyldimethoxysilane, 2- (meth) acrylamide-ethyldimethylmethoxysilane, 3- ( Meth) acrylamide-propylmethyldiacetoxysilane, 2- (meth) acrylamide-2-methylpropylhydrogendimethoxysilane, 3- (N-methyl- (meth) acrylamide) -propyltrimethoxy Silane, 2- (N-ethyl- (meth) acrylamide) -ethyltriacetoxysilane, etc. are mentioned.

  Among these monomers, 3- (meth) acrylamide-propyltrimethoxysilane and 3- (meth) acrylamide-propyltriacetoxysilane are preferably used because they are relatively easy to manufacture industrially and can be obtained at low cost. 2- (meth) acrylamido-2-methylpropyltrimethoxysilane and 2- (meth) acrylamide-2-methylpropyltriacetoxysilane are remarkably stable to acids or alkalis, It can be preferably used.

  Examples of a method for copolymerizing a monomer having a silyl group and a vinyl ester monomer include known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among these methods, a bulk polymerization method performed without a solvent or a solution polymerization method performed using a solvent such as alcohol is usually employed. When polymerizing by a bulk polymerization method or a solution polymerization method, the weight fraction of a polymer having a polymerization degree exceeding 3 times the weight average polymerization degree Pw is 25% by weight or less, and preferably the polymerization degree is a weight average polymerization. The polymerization method for obtaining the vinyl alcohol polymer of the present invention in which the weight fraction of the polymer smaller than ½ times the degree Pw is 12% by weight or less cannot be generally limited depending on the polymerization conditions and the like. From the viewpoint of suppressing the ratio of the degree component and the low degree of polymerization component, the continuous polymerization method is most preferable. As a continuous polymerization system, for example, a 1-2 tank continuous polymerization system is preferable, and a 1 tank continuous polymerization system is more preferable. In the case of the batch method, the ratio of the high polymerization degree component and the low polymerization degree component changes depending on the polymerization rate of the vinyl ester monomer, etc., and as the polymerization rate increases, the high polymerization degree component and the low polymerization degree component Since the ratio increases, it is preferable to polymerize at a relatively low polymerization rate. The suitable polymerization rate in the batch system cannot be defined unconditionally because it varies depending on the polymerization conditions and the like, but the polymerization rate of the vinyl ester monomer is preferably 10 to 80%, more preferably 15 to 50%. Examples of the alcohol used as a solvent when performing a copolymerization reaction by employing a solution polymerization method include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. Examples of the initiator used in the copolymerization reaction include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), 1,1′-azobis (cyclohexane- Azo initiators such as 1-carbonitrile) and 2,2′-azobis (N-butyl-2-methylpropionamide); peroxide initiators such as benzoyl peroxide and n-propyl peroxycarbonate A well-known initiator is mentioned. Although there is no restriction | limiting in particular about the polymerization temperature at the time of performing a copolymerization reaction, The range of 50-180 degreeC is suitable.

  When radically copolymerizing a monomer having a silyl group and a vinyl ester monomer, a copolymerizable monomer may be copolymerized as necessary as long as the effects of the present invention are not impaired. It can be polymerized. Examples of such monomers include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene; carboxylic acids such as fumaric acid, maleic acid, itaconic acid, maleic anhydride, and itaconic anhydride; Derivatives thereof; acrylic acid or salts thereof, acrylic esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate; methacrylic acid or salts thereof, methyl methacrylate, ethyl methacrylate, n methacrylate Methacrylic acid esters such as propyl and isopropyl methacrylate; Acrylamide derivatives such as acrylamide, N-methylacrylamide and N-ethylacrylamide; and methacrylamides such as methacrylamide, N-methylmethacrylamide and N-ethylmethacrylamide Body; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether; hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 1,4-butanediol vinyl ether Allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether, hexyl allyl ether; monomers having an oxyalkylene group; isopropenyl acetate, 3-buten-1-ol, 4-penten-1-ol Hydroxy group-containing α-olefins such as 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, 3-methyl-3-buten-1-ol; Monomers having sulfonic acid groups such as sulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid; vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyl Cationic groups such as dimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine And the like. The amount of the monomer having a silyl group and a monomer copolymerizable with the vinyl ester monomer varies depending on the purpose and use of the monomer, but all the monomers used for copolymerization are usually used. The ratio based on the monomer is 20 mol% or less, preferably 10 mol% or less.

  The vinyl ester polymer obtained by copolymerizing a monomer having a silyl group and a vinyl ester monomer is then saponified in a solvent according to a known method to give a vinyl alcohol polymer. Led.

  As a catalyst for the saponification reaction of a vinyl ester polymer, an alkaline substance is usually used. Examples thereof include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and alkali metal alkoxides such as sodium methoxide. Can be mentioned. The amount of the alkaline substance used is preferably in the range of 0.004 to 0.5 in terms of a molar ratio based on the vinyl ester monomer unit in the vinyl ester polymer. It is particularly preferable that the value falls within the range. The saponification catalyst may be added all at once in the early stage of the saponification reaction, or a part thereof may be added in the early stage of the saponification reaction, and the rest may be added and added during the saponification reaction.

  Examples of the solvent that can be used for the saponification reaction include methanol, methyl acetate, dimethyl sulfoxide, diethyl sulfoxide, dimethylformamide, and the like. Among these solvents, methanol is preferably used, and in its use, the water content of methanol is preferably 0.001 to 1% by weight, more preferably 0.003 to 0.9% by weight, and particularly preferably 0.005 to 0.005%. It should be adjusted to 0.8% by weight.

  The saponification reaction is preferably performed at a temperature of 5 to 80 ° C, more preferably 20 to 70 ° C. The time required for the saponification reaction is preferably 5 minutes to 10 hours, more preferably 10 minutes to 5 hours. The saponification reaction can be carried out by either a batch method or a continuous method. After completion of the saponification reaction, the remaining saponification catalyst may be neutralized as necessary, and examples of usable neutralizers include organic acids such as acetic acid and lactic acid, and ester compounds such as methyl acetate. Can do.

  The saponification degree of the vinyl alcohol polymer used in the present invention is not particularly limited, but the saponification degree is preferably 80 mol% or more, more preferably 85 mol% or more, particularly preferably 90 mol% or more. From the viewpoint of improving the water resistance of the film and suppressing calendar stains during the coating operation, the optimum degree of saponification of the vinyl alcohol polymer is 95 mol% or more.

  The vinyl alcohol polymer obtained by the saponification reaction can be washed if necessary, and this operation adjusts the value of (AB) / (B) in the vinyl alcohol polymer described above. Useful as a means. Usable cleaning liquids include lower alcohols such as methanol, lower fatty acid esters such as methyl acetate, and mixtures thereof. A small amount of water or an alkali or acid is added to these cleaning liquids. May be.

  The method employed for washing the vinyl alcohol polymer is the polymerization rate when the vinyl ester monomer and the monomer having a silyl group are copolymerized, and the vinyl ester polymer obtained by the copolymerization. It differs depending on the degree of polymerization, the degree of saponification of the vinyl alcohol polymer obtained by saponifying the vinyl ester polymer, and it is difficult to uniformly define this. As one of the methods, for example, it is obtained by saponifying a copolymer of a vinyl ester monomer and a monomer having a silyl group (vinyl ester polymer) in an alcohol solution, before drying. 1 to 20 times the amount of wet alcoholic polymer impregnated with alcohol or the like, a lower alcohol such as methanol, a lower fatty acid ester such as methyl acetate, or a mixture thereof as a washing solution, The method of washing for about 30 minutes to 10 hours under the temperature condition of the boiling point of the washing liquid can be mentioned.

  The vinyl alcohol polymer used in the present invention can be stored and transported in the form of a powder. In use, the vinyl alcohol polymer can be used in the form of a powder or dispersed in a liquid. it can. The vinyl alcohol polymer can be dissolved in water and used as an aqueous solution. In this case, the vinyl alcohol polymer is dispersed in water and then heated with stirring to obtain a uniform aqueous solution. can do. In this case, a uniform aqueous solution can be obtained without adding an alkali such as sodium hydroxide to water.

  The vinyl alcohol polymer used in the present invention can be dissolved in water to prepare an aqueous solution without adding an alkali or acid such as sodium hydroxide; the aqueous solution has excellent viscosity stability. The film obtained from the aqueous solution is excellent in water resistance; the film obtained from a mixture with an inorganic material is excellent in water resistance, etc. It can be used as a coating solution.

  When the silyl group-containing PVA described above is used for the coating layer, these coating liquids are filled with various polymers (water-soluble polymer, polymer emulsion, latex, etc.) as long as the object of the present invention is not impaired. An agent, a surfactant (nonionic or anionic), a lubricant, an antifoaming agent, a dispersing agent, a wetting agent, a pH adjusting agent, and an ultraviolet absorber can be appropriately blended depending on the use or performance.

  Examples of water-soluble polymers or polymer dispersions include starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, arabic gum, polyvinyl alcohol, and alkali salts of polyacrylic acid (soda salts, etc.) , Alkali salt (such as soda salt) of acrylic acid (or methacrylic acid) ester copolymer, polyvinylpyrrolidone, acrylamide (or methacrylamide) / acrylic acid (or methacrylic acid) ester copolymer, acrylamide (or methacrylamide) / Acrylic acid ester (or methacrylic acid ester) / acrylic acid (or methacrylic acid) terpolymer and alkali salt of styrene / maleic anhydride copolymer (soda salt) Highly water-soluble, such as alkali salts of isobutylene / maleic anhydride copolymer (soda salt, etc.), alkali salts of diisobutylene / maleic anhydride copolymer (soda salt, etc.), polyacrylamide, sodium alginate, gelatin, casein Molecule: Polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer emulsion, styrene / butadiene copolymer latex, styrene And latex such as / butadiene / acrylic copolymer.

  As filler, kaolin, clay, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, silica, colloidal silica, aluminum oxide, aluminum hydroxide, synthetic aluminum silicate, synthetic magnesium silicate, polystyrene fine particles, polyvinyl acetate series Examples thereof include fine particles, urea-formalin resin fine particles, and wheat flour.

  Further, a water-resistant agent such as glyoxal, urea resin, melamine resin, polyvalent metal salt, water-soluble polyamide resin can be added as necessary.

In the present invention, the concentration of the silyl group-containing PVA is not particularly limited, and is arbitrarily selected according to the coating amount (increase in the dry weight of the paper generated by coating), the apparatus used for coating, operating conditions, and the like. However, usually 1 to 15% by weight is used. Examples of the coating equipment include a 2-roll size press, a gate roll size press, a metering size press, an air knife coater, a bar coater, a roll coater, and a blade coater. The coating amount can be arbitrarily selected according to the properties of the paper, but about 0.3 to 3 g / m ² per one side of normal paper is particularly excellent. The coating solution is preferably an aqueous solution, and the aqueous solution viscosity is often about 10 to 3000 cps at 50 ° C. The coating solution does not prevent the use of other solvents than water.

  The coated paper can be dried by, for example, hot air, infrared rays, a heated cylinder, or a combination of these methods. The dried coated paper can be barrier-treated by humidity conditioning and calendering, particularly super calendering. It can be further improved. As humidity control conditions, it is desirable that the moisture content in the paper is 10 to 30% by weight. Moreover, as calendering conditions, the roll temperature is preferably from room temperature to 200 ° C. and the roll linear pressure from 20 to 350 kg / cm.

  In the present invention, the moisture content of the coated paper before supercalendering is preferably 10 to 30% by weight, more preferably 13 to 25% by weight, and particularly preferably 15 to 20% by weight. When the paper moisture content before supercalendering is less than 10% by weight, sufficient air permeability and toluene barrier performance may not be obtained, and when it exceeds 30% by weight, calendar stains are likely to occur.

  The air permeability of the release paper base paper obtained in the present invention can be achieved if the air permeability is 10,000 seconds or more, but is preferably 30,000 seconds or more, more preferably 50,000 seconds or more. It is preferable. When the air permeability is less than 10,000 seconds, the sealing effect on the topcoat coating agent on the release paper base paper is not sufficient, which is uneconomical. These topcoat coating agents include a release layer and an adhesive layer. Examples of the release agent used for the release layer include solvent-based silicones and non-solvent-based (emulsion-based and oligomer-based) silicones. The pressure-sensitive adhesive used for the topcoat layer of the release layer includes a solvent-based pressure-sensitive adhesive and an emulsion-based pressure-sensitive adhesive. In any case, when using a solvent system, barrier properties against the solvent (toluene, etc.) contained in the solvent system are required. When using an emulsion system, barrier properties against water and water resistance, especially water resistance, are required. Sexuality is required.

As the release paper base material used in the present invention, chemical pulp such as hardwood kraft pulp, conifer kraft pulp, mechanical pulp such as GP, RGP, TMP, etc. are used as raw materials, long net paper machine, long net Yankee type paper machine, Alternatively, it includes high quality paper, medium quality paper, and alkaline paper made by a round net paper machine. The base paper may contain organic and inorganic pigments and paper-making aids such as paper strength enhancers, sizing agents, yield improvers and the like. Note The basis weight preferably is selected from the range of 10 to 100 g / m ^2.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following examples and comparative examples, “parts” and “%” mean weight basis unless otherwise specified.

  First, PVA was produced by the following method, and the degree of saponification, the content of monomer units having a silyl group, the weight average degree of polymerization, and the content of silicon atoms were determined.

[Saponification degree of PVA]
The degree of saponification of PVA was determined by the method described in JIS K6726.

[Content of monomer unit having silyl group contained in PVA]
The vinyl ester polymer before saponification was purified by reprecipitation with hexane-acetone to completely remove the monomer having unreacted silyl groups from the polymer, followed by drying at 90 ° C. under reduced pressure for 2 days. Using a sample dissolved in a CDCl ₃ solvent as a measurement sample, the content of the monomer unit having a silyl group contained in PVA was determined using a 500 MHz proton NMR measurement apparatus (JEOL GX-500).

[Weight average polymerization degree of PVA]
A sample obtained by saponifying PVA to a saponification degree of 99.5 mol% or more was used as a sample, and a weight average molecular weight was determined by a LALLS (low angle laser light scattering photometer) method. Measurement was performed at 23 ° C. using a GPC224 type gel permeation chromatograph (Waters) connected with three TSK-gel-GMPWxL (manufactured by Tosoh Corporation) as a column. In the measurement, 0.08 M Tris buffer (pH 7.9) was used as a solvent, and an R-401 differential refractometer, 8X (Waters) was used as a detector. In order to obtain the absolute molecular weight of the sample, a KMX-6 type low angle laser light scattering photometer (Chromatix) is connected for measurement, and the weight average molecular weight obtained as a result of the measurement is expressed as a formula weight 44 of vinyl alcohol monomer units. The value obtained by dividing by was used as the weight average polymerization degree. The weight fraction of the polymer having a degree of polymerization exceeding 3 times the weight average degree of polymerization and the weight fraction of a polymer having a degree of polymerization smaller than ½ times the weight average degree of polymerization are obtained by the above measurement. Obtained from the obtained integral polymerization degree distribution.

[Content of silicon atom contained in PVA]
The content of silicon atoms contained in PVA was determined using an ICP emission analyzer IRIS AP manufactured by Jarrel Ashe according to the method described above.

PVA1
A polymerization tank equipped with a stirrer, a temperature sensor, a chemical addition line, a polymerization liquid take-out line and a reflux condenser is charged with 2500 parts of vinyl acetate, 1656 parts of methanol, and 752 parts of a methanol solution containing 2% by weight of vinyltrimethoxysilane (VMS). After charging and replacing the system with nitrogen under stirring, the internal temperature was raised to 60 ° C. To this system, 20 parts of methanol containing 0.1 part of 2,2′-azobis (4-methoxy-2,4-dimethoxyvaleronitrile) (AMV) was added to initiate the polymerization reaction. From the start of polymerization, polymerization was carried out while adding 100 parts of a methanol solution containing 2% by weight of VMS. At the same time, a methanol solution containing 0.13% by weight of AMV was added into the system at a rate of 23 parts / hour, and a polymerization reaction was carried out for 4 hours until the solid content concentration in the system reached 25%. From the time when the concentration of solids in the system reaches 25%, vinyl acetate 625 parts / hour, methanol 414 parts / hour, methanol solution 188 parts / hour containing 2% VMS, and AMV 0.13% While the methanol solution was added to the system at a rate of 23 parts / hour, the polymerization reaction was carried out while continuously taking out the polymerization solution from the system so that the liquid level in the polymerization tank was constant. When 4 hours had elapsed from the start of addition, the polymerization solution was recovered. By introducing methanol vapor into the recovered liquid, unreacted vinyl acetate monomer was driven off to obtain a methanol solution containing 40% vinyl ester polymer. The solid content concentration in the system at the time when the polymerization solution was recovered was 25%.

  For a methanol solution containing 40% of this vinyl ester polymer, the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.02, and the solid content concentration of the vinyl ester polymer is 35 wt. %, Methanol and a methanol solution containing 10% by weight of sodium hydroxide were added in this order under stirring, and the saponification reaction was started at 40 ° C.

Immediately after the saponification reaction has progressed, a gelled product is formed and removed from the reaction system and pulverized. Then, methyl acetate is added to the pulverized product when 1 hour has elapsed since the start of the saponification reaction. The PVA neutralized and swollen with methanol was obtained. To the PVA swollen with methanol, 6 times the amount of methanol (six times the bath ratio) of methanol was added, washed under reflux for 1 hour, and then dried at 65 ° C. for 16 hours to obtain PVA.
The obtained PVA had a vinyltrimethylsilane unit content of 0.50 mol%, a saponification degree of 98.5 mol%, and a weight average polymerization degree of 580. Moreover, the value of (AB) / (B) calculated | required according to the analysis method of silicon atom content contained in the above-mentioned PVA is 10.9 / 100, and pH of 4% PVA aqueous solution is 6.0. there were.

PVA2
PVA2 was prepared in the same manner as PVA1 except that the amounts of vinyl acetate and methanol, the amount of monomer having a silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction were changed as shown in Table 1. Was synthesized. Table 4 shows the results of analysis on the obtained PVA.

PVA3
In a polymerization tank 1 equipped with a stirrer, a temperature sensor, a chemical addition line, a polymerization liquid take-out line and a reflux condenser, and a polymerization tank 2 equipped with the same equipment, 2000 parts of vinyl acetate, 2352 parts of methanol, vinyltrimethoxysilane ( After adding 600 parts of a methanol solution containing 2% by weight of VMS) and replacing the system with nitrogen under stirring, the internal temperature was raised to 60 ° C. 20 parts of a methanol solution containing 0.05 part of 2,2′-azobis (4-methoxy-2,4-dimethoxyvaleronitrile) (AMV) is added to the polymerization tank 1 and the polymerization tank 2, respectively, and the polymerization reaction is carried out. Started. Polymerization was carried out while adding 80 parts of a methanol solution containing 2% by weight of VMS at a rate of 150 parts / hour from the start of polymerization to each polymerization tank. At the same time, a methanol solution containing 0.13% by weight of AMV was added to the polymerization tank 1 and the polymerization tank 2 at a rate of 4 parts / hour, and the polymerization reaction was continued for 4 hours until the solid content in the system reached 10%. went. Thereafter, the polymerization tank 1 was charged with 500 parts / hour of vinyl acetate, 588 parts / hour of methanol, 150 parts / hour of a methanol solution containing 2% of VMS, and 4 parts / hour of a methanol solution containing 0.13% of AMV. In the polymerization tank 2, the polymerization liquid is continuously taken out from the polymerization tank 1 and fed to the polymerization tank 2 so that the liquid level in the polymerization tank becomes constant. The polymerization reaction was carried out while continuously taking out the polymerization solution so that the liquid level inside was constant. In addition, when feeding the polymerization liquid taken out from the polymerization tank 1 to the polymerization tank 2, methanol containing 0.13% of AMV was added at a rate of 8 parts / hour.

  When 4 hours have elapsed from the start of the feed, when the solid content in the polymerization tank 1 is 10% and the solid content in the polymerization tank 2 is 24%, the polymerization solution is recovered from the polymerization tank 2 and recovered. By introducing methanol vapor into the resulting liquid, unreacted vinyl acetate monomer was driven off to obtain a methanol solution containing 40% vinyl ester polymer.

  For a methanol solution containing 40% of this vinyl ester polymer, the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.02, and the solid content concentration of the vinyl ester polymer is 35 wt. %, Methanol and a methanol solution containing 10% by weight of sodium hydroxide were added in this order under stirring, and the saponification reaction was started at 40 ° C.

  Immediately after the saponification reaction has progressed, a gelled product is formed and removed from the reaction system and pulverized. Then, methyl acetate is added to the pulverized product when 1 hour has elapsed since the start of the saponification reaction. The PVA neutralized and swollen with methanol was obtained. To the PVA swollen with methanol, 6 times the amount of methanol (six times the bath ratio) of methanol was added, washed under reflux for 1 hour, and then dried at 65 ° C. for 16 hours to obtain PVA.

  The obtained PVA had a vinyltrimethylsilane content of 0.50 mol%, a saponification degree of 98.2 mol%, and a weight average polymerization degree of 590. Moreover, the value of (AB) / (B) calculated | required according to the analysis method of silicon atom content contained in the above-mentioned PVA is 9.6 / 100, and pH of 4% PVA aqueous solution is 6.0. there were.

PVA4
Except for changing the amount of vinyl acetate and methanol, the amount of monomer having a silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction, etc. as shown in Table 2, PVA4 was synthesized by the same method. Table 4 shows the results of analysis on the obtained PVA.

PVA5
A 6 L separable flask equipped with a stirrer, a temperature sensor, a dropping funnel and a reflux condenser was charged with 1050 parts of vinyl acetate, 2056 parts of methanol, and 394 parts of a methanol solution containing 2% by weight of vinyltrimethoxysilane. Was replaced with nitrogen, and the internal temperature was raised to 60 ° C. To this system, 20 parts of methanol containing 1.3 parts of 2,2′-azobisisobutyronitrile was added to initiate the polymerization reaction. The polymerization reaction was carried out for 4 hours while adding 30 parts of a methanol solution containing 2% by weight of vinyltrimethoxysilane to the system from the start of the polymerization, and the polymerization reaction was stopped at that time. The solid concentration in the system at the time when the polymerization reaction was stopped was 15.2%. Subsequently, methanol vapor was introduced into the system to drive off unreacted vinyl acetate monomer, thereby obtaining a methanol solution containing 40% vinyl ester polymer.

  For a methanol solution containing 40% of this vinyl ester polymer, the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.02, and the solid content concentration of the vinyl ester polymer is 35 wt. %, Methanol and a methanol solution containing 10% by weight of sodium hydroxide were added in this order under stirring, and the saponification reaction was started at 40 ° C.

  Immediately after the saponification reaction has progressed, a gelled product is formed and removed from the reaction system and pulverized. Then, methyl acetate is added to the pulverized product when 1 hour has elapsed since the start of the saponification reaction. The PVA neutralized and swollen with methanol was obtained. To the PVA swollen with methanol, 6 times the amount of methanol (six times the bath ratio) of methanol was added, washed under reflux for 1 hour, and then dried at 65 ° C. for 16 hours to obtain PVA.

  The obtained PVA had a vinyltrimethylsilane content of 0.50 mol%, a saponification degree of 98.5 mol%, and a weight average polymerization degree of 560. Moreover, the value of (AB) / (B) calculated | required according to the analysis method of silicon atom content contained in the above-mentioned PVA is 10.9 / 100, and pH of 4% PVA aqueous solution is 6.0. there were.

PVA 6-9
Except for changing the amount of vinyl acetate and methanol, the type and amount of monomer having silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction, etc. as shown in Table 3. Various PVA (PVA6-9) was synthesize | combined by the method similar to PVA5. Table 4 shows the results of analysis on the obtained PVA.

PVA10
Saponification is performed by adding a methanol solution containing 10% by weight of sodium hydroxide to the vinyl ester polymer so that the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.01. PVA10 was synthesized in the same manner as PVA1 except that the reaction was performed. Table 4 shows the results of analysis on the obtained PVA.

PVA11
Saponification is performed by adding a methanol solution containing 10% by weight of sodium hydroxide to the vinyl ester polymer so that the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.01. PVA11 was synthesized in the same manner as PVA2 except that the reaction was performed. Table 4 shows the results of analysis on the obtained PVA.

PVA12
PVA12 was synthesized by the same method as PVA2, except that the washing operation with methanol was omitted. Table 4 shows the results of analysis on the obtained PVA.

PVA13
PVA13 was synthesized in the same manner as PVA2 except that a washing operation by Soxhlet extraction using methanol was added before neutralizing the PVA obtained by the saponification reaction with methyl acetate. Table 4 shows the results of analysis on the obtained PVA.

PVA14
PVA2 except that neutralization was performed using acetic acid having a molar number of 5 times that of sodium hydroxide used in the saponification reaction instead of methyl acetate, and further washing with methanol (bath ratio 6 times) was performed at room temperature for 1 hour. PVA14 was synthesized by the same method. Table 4 shows the results of analysis on the obtained PVA.

PVA15
PVA15 was synthesized by the same method as PVA2 except that neutralization with methyl acetate was not performed, and washing with methanol (bath ratio 6 times) was performed at room temperature for 1 hour. Table 4 shows the results of analysis on the obtained PVA.

PVA 16 and 17
PVA16 was prepared in the same manner as PVA1 except that the amounts of vinyl acetate and methanol, the amount of monomer having a silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction were changed as shown in Table 1. And 17 were synthesized. Table 4 shows the results of analysis on the obtained PVA.

PVA 18 and 19
Except for changing the amount of vinyl acetate and methanol, the amount of monomer having a silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction, etc. as shown in Table 2, PVA 18 and 19 were synthesized by the same method. Table 4 shows the results of analysis on the obtained PVA.

PVA 20 and 21
Except for changing the amount of vinyl acetate and methanol, the type and amount of monomer having silyl group, the amount of polymerization initiator used, the conditions for the polymerization reaction, the conditions for the saponification reaction, etc. as shown in Table 3. PVA20 and 21 were synthesized by the same method as PVA5. Table 4 shows the results of analysis on the obtained PVA.

PVA22
Saponification is performed by adding a methanol solution containing 10% by weight of sodium hydroxide to the vinyl ester polymer so that the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.01. PVA22 was synthesized in the same manner as PVA16 except that the reaction was performed. Table 4 shows the results of analysis on the obtained PVA.

PVA23
Saponification is performed by adding a methanol solution containing 10% by weight of sodium hydroxide to the vinyl ester polymer so that the molar ratio of sodium hydroxide to vinyl acetate units in the vinyl ester polymer is 0.01. PVA23 was synthesized in the same manner as PVA17 except that the reaction was performed. Table 4 shows the results of analysis on the obtained PVA.

Example 1
Using PVA1, the viscosity stability of the PVA aqueous solution and the water resistance of the film were evaluated by the following evaluation methods. Moreover, the PVA aqueous solution was coated under the conditions shown in Table 5 and subjected to the following evaluation. The results are summarized in Table 5.

(1) Viscosity stability of PVA aqueous solution A PVA aqueous solution with a concentration of 9% was prepared and allowed to stand in a 10 ° C constant temperature bath, and the viscosity immediately after the temperature of the PVA aqueous solution reached 10 ° C and the viscosity after 7 days were measured. . A value obtained by dividing the viscosity after 7 days by the viscosity immediately after the temperature of the aqueous PVA solution reached 10 ° C. (after 7 days / immediately) was determined and determined according to the following criteria.
A: Less than 2.5 times.
B: 2.5 times or more and less than 3.5 times.
C: 3.5 times or more.

(2) Water resistance of film A PVA aqueous solution having a concentration of 8% was prepared and cast at 20 ° C to obtain a film having a thickness of 40 µm. The obtained film was heat-treated at 120 ° C. for 10 minutes, and then cut into a size of 10 cm in length and 10 cm in width to prepare a test piece. This test piece was immersed in distilled water at 20 ° C. for 30 minutes, then taken out (collected), the water adhering to the surface was wiped off with gauze, and the weight at the time of water swelling was measured. The test piece whose weight during water swelling was measured was dried at 105 ° C. for 16 hours, and then the weight during drying was measured. Here, a value obtained by dividing the weight at the time of water swelling by the weight at the time of drying was obtained, and this was taken as the degree of swelling (times), and the determination was made according to the following criteria.
A: Less than 4.0 times.
B: 4.0 times or more and less than 5.0 times.
C: It is 5.0 times or more, or the immersed test piece cannot be collected.

(3) Coating and drying of coating liquid A glassy paper having a basis weight of 80 g / m ^{2 was} prepared using a test 2-roll size press machine (manufactured by Kumagai Riki Kogyo Co., Ltd.). Canadian Standard Freeness: 200 ml). The coating was performed at 50 ° C. under conditions of 100 m / min, and then dried at 110 ° C. for 1 minute to obtain a coated paper. The coating amount in terms of solid content of the coating solution was 1.8 g / m ² .

(4) Calendar treatment of coated paper The coated paper obtained in the above step (3) was conditioned for 72 hours with a thermo-hygrostat and the moisture content was adjusted to 17 wt% (measurement of moisture content) This was performed in accordance with JIS P8127). Then, a super calendar process (150 degreeC, 250 kg / cm, 10 m / min. 1 time process) was made, and it was set as the sample. The physical properties of this sample were measured.

(5) Evaluation of calendar dirt After passing the coated paper after humidity control in the above step (4) through the super calendar, the dirt on the chilled roll in the part in contact with the coated paper was visually determined according to the following criteria. .
Criteria ◎-There is no deposit on the surface of the chill roll. ○-There is a deposit on a part (less than half) of the surface of the chill roll. △-There is a deposit on about half of the surface of the chill roll. There is kimono

(6) Toluene barrier property Colored toluene (red) is applied on the coated surface of coated paper (5 x 5 cm) and then penetrated to the back surface (uncoated surface) (small red spots or the entire coated surface is colored) The degree of was determined according to the following criteria.
Standard ◎-No spots on the back surface ○-Many spots (about 10-20% of the surface where toluene is applied)
△-About 50% of the coated surface is colored ×-The entire coated surface is colored

(7) Air permeability of coated paper Measured using Oken type lubricity air permeability tester according to JIS P8117.

Example 2-7
Using PVA2~PVA 7, to evaluate the water resistance of the viscosity stability and film of PVA solution in the same manner as in Example 1. Moreover, the PVA aqueous solution was coated under the conditions shown in Table 5 and evaluated in the same manner as in Example 1. The results are summarized in Table 5.

Comparative Example 1-16
Using PVA 8 to PVA 23, the viscosity stability of the PVA aqueous solution and the water resistance of the film were evaluated in the same manner as in Example 1. Moreover, the PVA aqueous solution was coated under the conditions shown in Table 5 and evaluated in the same manner as in Example 1. The results are summarized in Table 5.

Examples 8-11
Using PVA2, the coating treatment was performed in the same manner as in Example 1 except that the moisture content of the paper during the calendar process was changed as shown in Table 5, and the evaluation was made in the same manner as in Example 1. The results are summarized in Table 5.

From the results in Table 5, it can be seen that the PVA aqueous solutions used in Examples 1 to 11 are excellent in viscosity stability and water resistance of the film. By using such a PVA aqueous solution, a coating operation with little calendar contamination is possible. Further, it was found that the obtained release paper base paper has high air permeability and excellent toluene barrier properties. In particular, the vinyl alcohol polymer satisfies the above formula (II) [0.1 / 100 ≦ (AB) / (B) ≦ 50/100], and the pH of a 4% aqueous solution of the vinyl alcohol polymer. Satisfying the conditions of 4 to 8 and the weight fraction of the polymer having a polymerization degree smaller than ½ times the weight average polymerization degree Pw in the vinyl alcohol polymer is 12% by weight or less. When the degree of saponification is 95 mol% or more (Examples 1 to 7 ), it can be seen that the further excellent balance is achieved.

  However, a vinyl alcohol polymer having Pw (weight average polymerization degree of vinyl alcohol polymer) × S (content of monomer unit having a silyl group) of 20 or less has decreased water resistance and air permeability. The toluene barrier property was also insufficient (Comparative Example 6). On the other hand, a vinyl alcohol polymer having Pw × S of 460 or more could not be evaluated because it was not completely dissolved in water (Comparative Example 5).

  Among the vinyl alcohol polymers, a vinyl alcohol polymer having a polymerization degree exceeding 3 times the weight average polymerization degree Pw and having a weight fraction exceeding 25% by weight is the viscosity stability of the aqueous solution and the water resistance of the film. It can be seen that the properties, air permeability and toluene barrier properties are not sufficient (Comparative Examples 3 and 4).

  It can be seen that the vinyl alcohol polymer containing no silyl group-containing monomer does not have sufficient water resistance, air permeability and toluene barrier property of the film (Comparative Examples 1, 2, 7 and 8).

In addition, as can be seen from a comparison between Examples 2 and 8 to 11 , when the moisture content before the calendar process becomes too high, a tendency for the dirt on the calendar to increase is recognized. However, in general, the higher the moisture content, the more the paper is crushed and the sealing effect is increased, and the best result was obtained when the moisture content was 17% (Example 2).

Claims (2)

The following general formula (1)

(R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have an oxygen-containing substituent, and m is 0 to 2 Is an integer.)
A vinyl alcohol polymer obtained by saponifying a vinyl ester polymer containing a monomer unit having a silyl group represented by the formula , satisfying the following formulas (I) and (II) , and saponifying The weight fraction of the polymer having a degree of 95% by mole or more, a pH of the 4% aqueous solution of 4 to 8, and a degree of polymerization exceeding 3 times the weight average degree of polymerization in the vinyl alcohol polymer. A vinyl alcohol polymer characterized in that the weight fraction of a polymer having a rate of 25% by weight or less and a polymerization degree smaller than ½ times the weight average polymerization degree is 12% by weight or less A release paper base paper having a coating layer formed on at least one surface of the release paper base.
20 <Pw × S <460 (I)
Pw: Weight average polymerization degree of vinyl alcohol polymer S: Content of monomer unit having silyl group represented by general formula (1) (mol%)
0.1 / 100 ≦ (A−B) / (B) ≦ 50/100 (II)
A: Content of silicon atom in vinyl alcohol polymer (unit: ppm)
B: Content of silicon atom in vinyl alcohol polymer washed with methanol containing sodium hydroxide and then washed with Soxhlet extraction with methanol (unit: ppm)
Here, A and B are measured by ICP emission spectrometry after ashing the measurement sample. The monomer having a silyl group is represented by the following general formula (2)

(Wherein R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have a substituent containing oxygen, and m is (It is an integer from 0 to 2, and n is an integer from 0 to 4.)
Or the following general formula (3)

(In the formula, R ¹ is an alkyl group having 1 to 5 carbon atoms, R ² is an alkoxyl group or an acyloxyl group, and these groups may have a substituent containing oxygen, and R ³ Is a hydrogen atom or a methyl group, R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁵ is an alkylene group having 1 to ⁵ carbon atoms, or 2 containing an oxygen atom or a nitrogen atom Is a valent hydrocarbon group, and m is an integer of 0 to 2.)
In the release paper sheet of claim 1, wherein the monomer represented.