JP6207921B2 - Vinyl acetal polymer - Google Patents

Description

  The present invention relates to a vinyl acetal polymer obtained by acetalizing a hydroxymethyl group-containing vinyl alcohol polymer having a vinylidene type 1,3-diol structure in the main chain.

  In general, a vinyl acetal polymer has a high elastic modulus, and when it is stretched or bent, a yield point appears in a low elongation region. In order to eliminate these drawbacks, a composition has been proposed in which a plasticizer is contained in a vinyl acetal polymer to lower the elastic modulus and have no yield point.

  However, the addition of a plasticizer to a vinyl acetal polymer cannot solve problems such as seepage of the plasticizer during use or volatilization of the plasticizer during use at high temperatures, and the use that can be used is limited. It was done.

  In synthesizing a vinyl acetal polymer, a vinyl alcohol polymer and an aldehyde are reacted by an acetalization reaction. Usually, only a vinyl acetal polymer having an acetalization degree of about 80 mol% is obtained. I can't. For this reason, there is a problem that the solubility in a low-polarity solvent is not sufficient and the use is limited.

  Under such circumstances, a polyvinyl alcohol resin containing a 1,2-diol component in the side chain is acetalized for the purpose of providing a polyvinyl acetal resin excellent in flexibility and solubility in an alcohol solvent. The polyvinyl acetal type resin which was made is disclosed (for example, refer patent documents 1-3). However, the methods described in Patent Documents 1 to 3 cannot sufficiently reduce the elastic modulus. Further, the degree of acetalization could not be sufficiently increased, and the solubility in a low polarity solvent was not sufficient. Specifically, the polyvinyl acetal resins described in Patent Documents 1 to 3 could not achieve both a decrease in elastic modulus when not containing the plasticizer and good solubility in a low-polarity solvent.

JP 2006-104309 A JP 2007-297613 A JP 2011-132120 A

  The object of the present invention is to solve the above-described problems. That is, the present invention is excellent in solubility in an alcohol solvent and a low polarity solvent, and the viscosity of a solution obtained by dissolving a vinyl acetal polymer in these solvents is kept low, and the vinyl acetal polymer is excellent in handleability. The purpose is to provide. Another object of the present invention is to provide a vinyl acetal polymer that has a moderately low elastic modulus and does not have a yield point in a low elongation region without containing a plasticizer.

で示される構造単位を含むヒドロキシメチル基含有ビニルアルコール系重合体をアセタール化して得られ、アセタール化度４５〜９０モル％である、ビニルアセタール系重合体を提供することによって解決される。 The above issues are vinyl alcohol units and formula (1):

It is solved by providing a vinyl acetal polymer obtained by acetalizing a hydroxymethyl group-containing vinyl alcohol polymer containing a structural unit represented by formula (1) and having an acetalization degree of 45 to 90 mol%.

  As a result of intensive studies by the present inventors, vinyl obtained by acetalizing a hydroxymethyl group-containing vinyl alcohol polymer having a 1,3-diol structure in the main chain and having a degree of acetalization of 45 to 90 mol% The present inventors have found that the above problems can be solved by using an acetal polymer, and have further studied based on the findings to complete the present invention.

または式（２）：

（式中、Ｒ^１は水素、直鎖状又は分岐を有する炭素数１〜８のアルキル基又はフェニル基である）で示される構造単位を含み、アセタール化度４５〜９０モル％である、ビニルアセタール系重合体；
［６］式（２）で示される構造単位を含む、前記［５］のビニルアセタール系重合体に関する。 That is, the present invention
[1] A vinyl acetal obtained by acetalizing a vinyl alcohol unit and a hydroxymethyl group-containing vinyl alcohol polymer containing the structural unit represented by the formula (1) and having a degree of acetalization of 45 to 90 mol% Based polymers;
[2] The vinyl acetal system of [1], obtained by acetalizing a hydroxymethyl group-containing vinyl alcohol polymer in which the content of the structural unit represented by the formula (1) is 0.1 to 30 mol% Polymer;
[3] The vinyl acetal polymer according to [1] or [2] obtained by acetalizing a hydroxymethyl group-containing vinyl alcohol polymer having a saponification degree of 80 to 99.9 mol%;
[4] The vinyl acetal polymer according to any one of [1] to [3], wherein the degree of acetalization is 80 to 90 mol%;
[5] At least formula (1):

Or formula (2):

(Wherein R ¹ is hydrogen, a linear or branched alkyl group having 1 to 8 carbon atoms or a phenyl group), vinyl having a degree of acetalization of 45 to 90 mol% An acetal polymer;
[6] The vinyl acetal polymer according to the above [5], which includes a structural unit represented by the formula (2).

  According to the present invention, it is possible to provide a vinyl acetal polymer that has a moderately low elastic modulus and does not have a yield point in the low elongation region without containing a plasticizer. Further, a vinyl acetal polymer having an acetalization degree exceeding 80 mol% can be economically provided without using a special synthesis method. As a result, there is provided a vinyl acetal polymer that is excellent in solubility in alcohol solvents and low polarity solvents, and that has a low viscosity of a solution obtained by dissolving a vinyl acetal polymer in these solvents, and that is excellent in handleability. be able to.

に示される構造単位を有する。 The hydroxymethyl group-containing vinyl alcohol polymer for producing the vinyl acetal polymer of the present invention has the formula (1):

The structural unit shown in FIG.

  The hydroxymethyl group-containing vinyl alcohol polymer for producing the vinyl acetal polymer of the present invention has a structural unit represented by the formula (1) (that is, a 1,3-diol structure in the main chain of the polymer). By having the structure having), the crystallinity of the vinyl alcohol polymer can be lowered, and the handleability such as solubility and viscosity stability in the acetalization step can be improved.

  The content of the structural unit represented by the formula (1) in the hydroxymethyl group-containing vinyl alcohol polymer for producing the vinyl acetal polymer of the present invention is not particularly limited, but in order to achieve the effects of the present invention The total structural unit in the vinyl alcohol polymer before acetalization is 100 mol%, preferably 0.1 to 30 mol%, more preferably 0.2 to 20 mol%, More preferably, it is 3 to 10 mol%.

  The viscosity average polymerization degree measured according to JIS K6726 of the hydroxymethyl group-containing vinyl alcohol polymer for producing the vinyl acetal polymer of the present invention is not particularly limited. The viscosity-average polymerization degree of the hydroxymethyl group-containing vinyl alcohol polymer is preferably 100 to 7,000, more preferably 200 to 5,000, and still more preferably 200 to 4,000. When the viscosity average degree of polymerization is less than 100, the film strength of the film may be lowered when the film is formed. A hydroxymethyl group-containing vinyl alcohol polymer having a viscosity average degree of polymerization exceeding 7,000 is difficult to produce industrially.

  Degree of saponification of the hydroxymethyl group-containing vinyl alcohol polymer for producing the vinyl acetal polymer of the present invention (that is, the mole fraction of hydroxyl groups relative to the total of hydroxyl groups and ester bonds in the hydroxymethyl group-containing vinyl alcohol polymer) (Rate) is not particularly limited, but is preferably 80 to 99.9 mol%, more preferably 90 to 99.5 mol%, from the viewpoint of film strength under high humidity. When the saponification degree is less than 80 mol%, sufficient film strength may not be obtained when the vinyl acetal polymer is formed into a film. Vinyl alcohol polymers having a saponification degree higher than 99.9 mol% are generally difficult to produce.

で表される化合物が挙げられる。式（３）において、Ｒ^２及びＲ^３は炭素数１〜１０のアルキル基を示し、同じ基であっても、異なる基であってもよい。Ｒ^２及びＲ^３の構造としては特に限定されず、一部に分岐、環状構造を有していてもよい。Ｒ^２及びＲ^３は好ましくは炭素数１〜５のアルキル基であり、具体例としては、メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ｔｅｒｔ−ブチル基、ペンチル基などの直鎖または分岐を有するアルキル基が挙げられる。また、Ｒ^２及びＲ^３は、アルキル基の炭素原子に結合している水素原子の一部が他の官能基で置換されていてもよい。このような置換基としては、アルコキシ基、ハロゲン原子、水酸基などが挙げられる。 The method for producing a hydroxymethyl group-containing vinyl alcohol polymer for producing the vinyl acetal polymer of the present invention is not particularly limited. For example, a copolymer obtained by copolymerizing a vinyl ester monomer and an unsaturated monomer that can be copolymerized therewith and can be converted into the structural unit represented by the formula (1). A structural unit derived from an unsaturated monomer capable of converting a vinyl ester unit of a polymer into a vinyl alcohol unit and capable of being converted into a structural unit represented by formula (1) is represented by formula (1). The method of converting into a structural unit is mentioned. Examples of the unsaturated monomer that can be converted into the structural unit represented by the formula (1) include the formula (3):

The compound represented by these is mentioned. In Formula (3), R ² and R ³ represent an alkyl group having 1 to 10 carbon atoms, and may be the same group or different groups. The structure of R ² and R ³ is not particularly limited, and may partially have a branched or cyclic structure. R ² and R ³ are preferably alkyl groups having 1 to 5 carbon atoms. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. And a linear or branched alkyl group such as a pentyl group. In R ² and R ³ , a part of the hydrogen atom bonded to the carbon atom of the alkyl group may be substituted with another functional group. Examples of such a substituent include an alkoxy group, a halogen atom, and a hydroxyl group.

  Examples of the unsaturated monomer represented by the formula (3) include 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyryloxy-2. -Methylenepropane and the like. Among these, 1,3-diacetoxy-2-methylenepropane is preferably used because it is easy to produce.

  The unsaturated monomer represented by the formula (3) is a vinyl ester type as compared with other allylic unsaturated monomers (for example, allyl glycidyl ether) generally used for modification of vinyl alcohol polymers. Copolymerization reaction with monomers tends to proceed. Accordingly, the hydroxymethyl group-containing vinyl alcohol polymer has few restrictions on the amount of modification and the degree of polymerization during polymerization, and can increase the amount of modification and the degree of polymerization. In addition, since the hydroxymethyl group-containing vinyl alcohol polymer has a small amount of the unreacted unsaturated monomer remaining at the end of the polymerization, there is little influence on the environment when industrially produced, and the production It is also excellent in terms of cost.

  The vinyl ester monomer used for the production of the hydroxymethyl group-containing vinyl alcohol polymer for producing the vinyl acetal polymer of the present invention is not particularly limited. For example, vinyl formate, vinyl acetate, vinyl propionate, Vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate. Among these, vinyl acetate is preferable from the viewpoint of production cost.

  The polymerization method for copolymerizing the unsaturated monomer represented by formula (3) and the vinyl ester monomer may be any of batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. Known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be applied. A bulk polymerization method or a solution polymerization method in which polymerization is allowed to proceed in a solvent-free or solvent such as alcohol is usually employed. In order to obtain a vinyl ester copolymer having a high degree of polymerization, one of the options is to employ an emulsion polymerization method. Although the solvent of a solution polymerization method is not specifically limited, For example, alcohol is mentioned. The alcohol used as the solvent for the solution polymerization method is, for example, a lower alcohol such as methanol, ethanol, or propanol. The amount of the solvent used in the polymerization system may be selected in consideration of the chain transfer of the solvent according to the viscosity-average polymerization degree of the target hydroxymethyl group-containing vinyl alcohol polymer. For example, when the solvent is methanol, the amount of the solvent used is 0.01 to 10 in mass ratio {= (solvent) / (total monomer)} between the solvent and the total monomer contained in the polymerization system. The range may be adjusted, preferably 0.05 to 3.

  The polymerization initiator used for the copolymerization of the unsaturated monomer represented by the formula (3) and the vinyl ester monomer is a known polymerization initiator such as an azo initiator or a peroxide initiator. An agent and a redox initiator are selected according to the polymerization method. Examples of the azo initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4). -Dimethylvaleronitrile). Examples of the peroxide initiator include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate, α- Perester compounds such as cumylperoxyneodecanate; acetyl peroxide; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate. Caryl persulfate, ammonium persulfate, hydrogen peroxide, or the like may be combined with the above initiator to form a polymerization initiator. The redox initiator is, for example, a polymerization initiator in which the peroxide initiator is combined with a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, or longalite.

  The amount of the polymerization initiator used varies depending on the polymerization catalyst and is not generally determined, but is selected according to the polymerization rate. For example, when azobisisobutyronitrile or acetyl peroxide is used as the polymerization initiator, the amount of the polymerization initiator used may be 0.01 to 0.2 mol% with respect to the vinyl ester monomer. Preferably, it is 0.02-0.15 mol%. The polymerization temperature is not particularly limited, but is suitably about room temperature to 150 ° C., preferably 40 ° C. or higher and lower than the boiling point of the solvent used.

  The copolymerization of the unsaturated monomer represented by the formula (3) and the vinyl ester monomer may be performed in the presence of a chain transfer agent as long as the effect of the present invention is obtained. Examples of the chain transfer agent include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; phosphinic acid salts such as sodium phosphinate monohydrate and the like. Of these, aldehydes and ketones are preferably used. The amount of chain transfer agent added to the polymerization system is determined according to the chain transfer coefficient of the chain transfer agent to be added and the degree of polymerization of the target hydroxymethyl group-containing vinyl alcohol polymer. It is preferable that it is 0.1-10 mass parts with respect to 100 mass parts of monomers.

  Saponifying a vinyl ester copolymer obtained by copolymerization of an unsaturated monomer represented by formula (3) and a vinyl ester monomer to obtain a hydroxymethyl group-containing vinyl alcohol polymer. Can do. By saponifying the vinyl ester copolymer, the vinyl ester unit in the copolymer is converted to a vinyl alcohol unit. Moreover, the ester bond of the unit derived from the unsaturated monomer represented by the formula (3) is also hydrolyzed and converted into a 1,3-diol structure represented by the formula (1). Therefore, the hydroxymethyl group-containing vinyl alcohol polymer in the present invention can be produced without further reaction such as hydrolysis after saponification.

  The saponification of the vinyl ester copolymer is performed, for example, in a state where the vinyl ester copolymer is dissolved in alcohol or hydrous alcohol. Examples of the alcohol used for saponification include lower alcohols such as methanol and ethanol. Of these, methanol is preferable. The solvent used for saponification may be a solvent such as acetone, methyl acetate, ethyl acetate, or benzene as long as it is 40% by mass or less of the total mass of alcohol.

  Examples of the catalyst used for saponification include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, alkali catalysts such as sodium methylate, and acid catalysts such as mineral acid. Of these, sodium hydroxide is preferred because it can be used industrially at low cost and the remaining metal ions hardly affect the mechanical properties of the vinyl acetal polymer.

  Although the temperature which performs saponification is not limited, the range of 20-60 degreeC is suitable. When a gel-like product is precipitated as saponification progresses, it is preferable to further saponify after pulverizing the product. Then, saponification is complete | finished by neutralizing the obtained solution, and it can wash | clean and dry, and can obtain a hydroxymethyl group containing vinyl alcohol polymer. The saponification method is not limited to the method described above, and a known method can be applied.

  The hydroxymethyl group-containing vinyl alcohol polymer used in the present invention further has a structural unit other than the structural unit represented by the formula (1), the vinyl alcohol unit and the vinyl ester unit as long as the effects of the present invention are obtained. Can do. The structural unit can be copolymerized with, for example, a vinyl ester, and can be converted to a structural unit represented by the formula (1), and can be copolymerized with an unsaturated monomer and a vinyl ester monomer. A structural unit derived from an unsaturated monomer. Examples of the ethylenically unsaturated monomer include α-olefins such as ethylene, propylene, n-butene, isobutylene and 1-hexene; acrylic acid and salts thereof; unsaturated monomer having an acrylate group. Methacrylic acid and salts thereof; unsaturated monomer having a methacrylic ester group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid and salts thereof; Acrylamidepropyldimethylamine and its salts (eg quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts (eg Quaternary salt); methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1 -Vinyl ethers such as vinyloxypropane; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl acetate; Allyl compounds such as 2,3-diacetoxy-1-allyloxypropane and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid and fumaric acid and salts or esters thereof; vinyl trime Examples thereof include vinylsilyl compounds such as toxisilane and isopropenyl acetate.

  The arrangement order of the structural unit represented by the formula (1), the vinyl alcohol unit and other arbitrary structural units in the hydroxymethyl group-containing vinyl alcohol polymer for producing the vinyl acetal polymer of the present invention is not particularly limited. There may be any of random, block, and alternating.

  The vinyl acetal polymer of the present invention can be obtained by acetalizing the vinyl alcohol polymer obtained as described above according to a conventionally known method. In this case, the degree of acetalization needs to be 45 to 90 mol%. By setting the degree of acetalization within the above range, the vinyl acetal polymer can sufficiently exhibit various characteristics derived from a hydroxymethyl group, and has solubility in an alcohol solvent and a low polarity solvent. Can be improved. The degree of acetalization of the vinyl acetal polymer is preferably 55 to 90 mol%, more preferably 60 to 90 mol%. Furthermore, from the viewpoint of excellent solubility in relatively low polarity solvents such as terpineol, dihydroterpineol, and dihydroterpinyl acetate, the degree of acetalization of the vinyl acetal polymer is 75 to 90 mol%. Is particularly preferred, with 80 to 90 mol% being most preferred. In order to adjust the degree of acetalization of the vinyl acetal polymer, the amount of aldehyde or acid catalyst added to the hydroxymethyl group-containing vinyl alcohol polymer, the reaction time after adding the aldehyde and acid catalyst, etc. can be adjusted as appropriate. Good. In order to obtain a vinyl acetal polymer having a high degree of acetalization, it is preferable to acetalize a vinyl alcohol polymer having a high degree of saponification.

Here, the degree of acetalization of the vinyl acetal polymer represents the total number of moles of acetalized vinyl alcohol units and hydroxymethyl groups with respect to the number of moles of all monomer units constituting the vinyl acetal polymer. . The degree of acetalization can be measured in accordance with, for example, the method of JIS K6728 (1977). Ordinary polyvinyl alcohol, for example, has a segment in which five vinyl alcohol units are continuous. When two vinyl alcohol units are acetalized at both ends of this segment, The hydroxyl group possessed will remain without being acetalized. If it is a hydroxymethyl group-containing vinyl alcohol polymer used in the present invention, if the structural unit represented by the formula (1) is present at any of the second, third and fourth positions from the ends of five consecutive segments, Even if the vinyl alcohol unit is acetalized at both ends of this segment, the hydroxyl group of the isolated vinyl alcohol unit (or the structural unit represented by the formula (1)) in the center of this segment is between adjacent units (or And within the structural unit represented by formula (1)) can be further acetalized. As a result, the degree of acetalization can be increased.
Furthermore, as the acetalization reaction proceeds, recombination of the acetal ring occurs, but the fact that the vinyl acetal polymer of the present invention tends to increase the degree of acetalization also has many choices of hydroxyl groups that can undergo recombination.

  As a method for acetalizing a hydroxymethyl group-containing vinyl alcohol polymer, for example, (1) a hydroxymethyl group-containing vinyl alcohol polymer is heated and dissolved in water to prepare an aqueous solution having a concentration of 5 to 30% by mass. A method of starting acetalization by cooling the solution to 5 to 50 ° C., adding a predetermined amount of aldehyde, cooling to −10 to 30 ° C., and adding an acid to bring the pH of the aqueous solution to 1 or less. (2) By heating and dissolving the hydroxymethyl group-containing vinyl alcohol polymer in water to prepare an aqueous solution having a concentration of 5 to 30% by mass, cooling the solution to 5 to 50 ° C., and adding an acid A method of starting acetalization by adding a predetermined amount of aldehyde after cooling the aqueous solution to pH 1 or less and then cooling to −10 ° C. to 30 ° C. can be mentioned.

  Examples of the aldehyde used for acetalization include formaldehyde (including paraformaldehyde), acetaldehyde (including paraacetaldehyde), propionaldehyde, butyraldehyde, isobutyraldehyde, 2-ethylbutyraldehyde, valeraldehyde, pivalaldehyde, and amylaldehyde. , Hexyl aldehyde, heptyl aldehyde, 2-ethylhexyl aldehyde, octyl aldehyde, nonyl aldehyde, decyl aldehyde, aliphatic aldehyde such as dodecyl aldehyde; cyclopentane aldehyde, methyl cyclopentane aldehyde, dimethyl cyclopentane aldehyde, cyclohexane aldehyde, methyl cyclohexane aldehyde, Dimethylcyclohexanealdehyde, cyclohexaneacetoaldehyde Cyclic unsaturated aldehydes such as cyclopentene aldehyde and cyclohexene aldehyde; benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, dimethylbenzaldehyde, methoxybenzaldehyde, phenylacetaldehyde, β-phenylpropion Aromatic or unsaturated bond-containing aldehydes such as aldehyde, cuminaldehyde, naphthylaldehyde, anthraldehyde, cinnamaldehyde, crotonaldehyde, acroleinaldehyde, 7-octen-1-al; heterocyclic aldehydes such as furfural and methylfurfural It is done.

  Among these, at least one selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde, and benzaldehyde is preferable, and butyraldehyde is particularly preferable. By using such an aldehyde, it is possible to more efficiently acetalize the hydroxymethyl group-containing vinyl alcohol polymer, and the resulting vinyl acetal polymer has a reduced elastic modulus and contains a plasticizer. Without having a yield point in the low elongation region without it.

  Moreover, you may perform acetalization using the aldehyde which has functional groups, such as a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, and an amino group, in the range which does not impair the effect of this invention. Alternatively, acetalization may be performed using an aldehyde having the functional group as a protected group.

  Although it does not specifically limit as an acid used for acetalization, For example, an acetic acid, p-toluenesulfonic acid, nitric acid, a sulfuric acid, hydrochloric acid etc. are mentioned. Among these, hydrochloric acid, sulfuric acid, and nitric acid are preferable, hydrochloric acid and nitric acid are more preferable, and two or more of these may be used in combination.

  The time required for the acetalization reaction is usually about 1 to 10 hours, and the reaction is preferably carried out with stirring. Moreover, when acetal is performed under the above-described temperature conditions, the reaction may be continued at a high temperature of about 50 ° C. to 80 ° C. if the degree of acetalization of the vinyl acetal polymer does not increase.

  The granular reaction product obtained after the acetalization is filtered off, washed thoroughly with water, added with a neutralizing agent such as alkali, washed and dried to obtain the desired vinyl acetal polymer. . Examples of the alkali compound used as a neutralizing agent include sodium hydroxide and potassium hydroxide.

The vinyl acetal polymer of the present invention thus produced contains at least a structural unit represented by formula (1) or formula (2). Formula (2) is a structural unit obtained by an acetalization reaction between the vinyl alcohol unit and the structural unit represented by Formula (1). R ¹ is preferably hydrogen, a methyl group, an ethyl group, a propyl group, a pentyl group or a phenyl group, and particularly preferably a propyl group.

  The vinyl acetal polymer of the present invention thus produced has excellent solubility in alcohol solvents and low polarity solvents, and the viscosity of a solution obtained by dissolving the vinyl acetal polymer in these solvents is kept low. And is easy to handle. Further, a vinyl acetal polymer having a moderately low elastic modulus and having no yield point in the low elongation region without containing a plasticizer is provided. The vinyl acetal polymer of the present invention further includes a filler, a processing stabilizer such as a copper compound, a weather resistance stabilizer, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, and a flame retardant. , Plasticizers, other thermoplastic resins, lubricants, fragrances, defoamers, deodorants, extenders, release agents, mold release agents, reinforcing agents, crosslinking agents, fungicides, preservatives, crystallization rate delay An additive such as an agent can be appropriately blended as necessary. Accordingly, the vinyl acetal polymer of the present invention comprises a laminated glass interlayer film composition, a solar cell sealant, a ceramic slurry composition, an ink composition / coating composition, an adhesive composition, a heat-developable photosensitive resin. It is suitably used for various applications such as material compositions.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples. Hereinafter, the vinyl alcohol polymer may be abbreviated as PVA. Also, the vinyl acetal polymer may be abbreviated as VAP. In the examples and comparative examples, “%” and “parts” represent “% by mass” and “parts by mass”, respectively, unless otherwise specified.

<Evaluation of vinyl alcohol polymer>
The vinyl alcohol polymer obtained in each example and comparative example was evaluated by the following method.

(Degree of polymerization)
The viscosity average polymerization degree P of the vinyl alcohol polymer was measured according to JIS K6726. When the saponification degree is less than 99.5 mol%, 1 g of the re-saponified vinyl alcohol polymer is added to 100 ml of water and dissolved by heating until the saponification degree is 99.5 mol% or more, and then cooled to 30 ° C. . The obtained aqueous solution was weighed in a viscometer, and the intrinsic viscosity [η] (g / dl) measured at 30 ° C. was measured. From the intrinsic viscosity [η], the viscosity average degree of polymerization (P) was calculated by the following formula (a).

(Measurement of denaturation)
The primary structure of the vinyl alcohol polymer was measured by ¹ H-NMR at 500 MHz. More specifically, 0.3 mg of vinyl alcohol polymer was dissolved in 3 ml of deuterated DMSO, and ¹ H-NMR measurement was performed using a nuclear magnetic resonance apparatus (LAMDA500, manufactured by JEOL Ltd.). did. From the obtained spectrum, the introduction amount (modification amount) of the structural unit represented by the formula (1) with respect to all the structural units of the vinyl alcohol polymer was measured.

(Measurement of saponification degree)
The vinyl alcohol polymer was measured by a saponification degree measuring method described in JIS K6726.

<Evaluation of vinyl acetal polymer>
The vinyl acetal polymer obtained in each Example and Comparative Example was evaluated by the following method.

(Measurement of degree of acetalization)
The degree of acetalization of the vinyl acetal polymer was analyzed according to the method described in JIS K6728.

(Solubility and solution viscosity of vinyl acetal polymer)
For each vinyl acetal polymer, a 5% by mass ethanol / water (95% / 5%) solution was prepared, and the solubility of each vinyl acetal polymer was visually observed. Those that were completely dissolved were evaluated as “◯”, and those that were not completely dissolved were evaluated as “×”. The results are shown in Table 2. When the vinyl acetal polymer is completely dissolved, the resulting solution is left in a constant temperature bath at 20 ° C. for 2 hours or longer, and the viscosity (mPa · s) of the solution is measured using a Brookfield viscometer. ) Was measured.

  For each vinyl acetal polymer, a 5% by mass dihydroterpineol solution was prepared, and the solubility of each vinyl acetal polymer was visually observed. Those that were completely dissolved were evaluated as “◯”, and those that were not completely dissolved were evaluated as “×”. The results are shown in Table 2. When the vinyl acetal polymer is completely dissolved, the resulting solution is left in a constant temperature bath at 20 ° C. for 2 hours or longer, and the viscosity (mPa · s) of the solution is measured using a Brookfield viscometer. ) Was measured.

(Mechanical properties of vinyl acetal polymer)
For each of the vinyl acetal polymers obtained in each Example and Comparative Example, a cast film was formed using an ethanol / water (95% / 5%) solution having a vinyl acetal polymer concentration of 10% by mass. The film was vacuum-dried at 50 ° C. for 15 hours by the method to produce a film having a thickness of 100 μm. The obtained film was subjected to a tensile test according to JIS K7162. More specifically, a film having a thickness of 100 μm was cut into a dumbbell shape, and this was subjected to a tensile test with a tensile tester (manufactured by Shimadzu Corporation, Autograph AG-IS) at a tensile speed of 50 mm / min. Yield point elongation and maximum elongation were measured. For each example and comparative example, five test pieces were prepared, and the average values thereof were determined as the yield point elongation and the maximum elongation.

[Example 1]
A reactor equipped with a stirrer, a reflux condenser, an argon inlet, and an initiator addition port was charged with 640 g of vinyl acetate, 223 g of methanol, and 6.43 g of 1,3-diacetoxy-2-methylenepropane (DAMP) as a comonomer. The system was purged with argon for 30 minutes while carrying out argon bubbling. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.15 g of 2,2′-azobisisobutyronitrile (AIBN) was added to initiate polymerization. After polymerization at 60 ° C. for 218 minutes, the polymerization was stopped by cooling. The polymerization rate when the polymerization was stopped was 40%. Subsequently, unreacted monomers were removed while adding methanol occasionally at 30 ° C. under reduced pressure, and a methanol solution (concentration of vinyl acetate-1,3-diacetoxy-2-methylenepropane copolymer (DAMP-modified PVAc)) 33.5%).

  Next, 95.8 g of methanol is added to 149 g of this methanol solution (the DAMP-modified PVAc in the solution is 50 g), and 4.72 g of sodium hydroxide methanol solution (concentration: 13.3%) is further added. Saponification was performed at 40 ° C. (the concentration of DAMP-modified PVAc in the saponified solution was 20%, and the molar ratio of sodium hydroxide to vinyl acetate units in the DAMP-modified PVAc was 0.03). After adding the sodium hydroxide methanol solution, a gelled product was formed in about 7 minutes. This was pulverized by a pulverizer and further allowed to stand at 40 ° C. for 53 minutes to proceed saponification, and then 200 g of methyl acetate was added. In addition, the remaining alkali was neutralized. After confirming the completion of neutralization using a phenolphthalein indicator, the mixture was filtered to obtain a white solid. Methanol 500g was added to the obtained white solid, and it heated and refluxed for 1 hour. After repeating the above washing operation three times, the white solid obtained by centrifugal dehydration is dried in a vacuum dryer at 40 ° C. for 24 hours, and contains a hydroxymethyl group containing the structural unit represented by formula (1) A vinyl alcohol polymer PVA-1 was obtained. The degree of polymerization was 1700, the degree of saponification was 98.7 mol%, and the modification amount (that is, the content of the structural unit represented by the formula (1) in the hydroxymethyl group-containing vinyl alcohol polymer) was 0.9 mol%. It was. Table 2 shows the physical properties of PVA-1.

(Synthesis of vinyl acetal polymer)
480 g of PVA-1 was put into 5,520 mL of water, and the temperature of the solution was increased to 90 ° C. with stirring and dissolved, and then cooled to 30 ° C. To this aqueous solution, 400 g of a 20% strength hydrochloric acid aqueous solution was added. Thereafter, the aqueous solution was cooled to 14 ° C., and 267 g of butyraldehyde was added dropwise over 10 minutes to initiate the reaction. After reacting at 14 ° C. for 40 minutes, the temperature was raised to 65 ° C. at a temperature raising rate of about 0.6 ° C./min, and maintained at 65 ° C. for 300 minutes. Thereafter, the reaction solution was cooled to room temperature, the precipitated particulate matter was filtered off, and this was sufficiently washed with water. The obtained product was put into a 0.3% sodium hydroxide solution and neutralized by heating to 70 ° C. Subsequently, after washing with water to remove the alkaline compound, the product was dried to obtain a vinyl acetal polymer (VAP-1). When the degree of acetalization of the obtained vinyl acetal polymer was analyzed according to the method described in JIS K6728, it was 71.5 mol%. Further, the viscosity of 5% by mass of ethanol / water (95% / 5%) of the obtained vinyl acetal polymer was a value shown in Table 2.

  In addition, when a film having a thickness of 100 μm was prepared by a cast film forming method using a 5% by mass ethanol / water (95% / 5%) solution, the film was pulled at a pulling speed of 50 mm / min in accordance with JIS K7162. Yield point elongation and maximum elongation were measured. Yield point elongation and maximum elongation are shown in Table 2.

[Examples 2 to 7]
Table 1 shows the saponification conditions such as the amount of vinyl acetate and methanol charged, the polymerization conditions such as the type and amount of comonomer used during polymerization, the concentration of modified PVAc during saponification, and the molar ratio of sodium hydroxide to vinyl acetate units. PVA-2 to PVA-7 were produced in the same manner as in Example 1 except that the change was made as described above. Table 2 shows the physical properties of each PVA.

  A vinyl acetal polymer VAP- was used in the same manner as in Example 1 except that PVA-2 to PVA-7 were used instead of PVA-1 and the amount of butyraldehyde added was changed as shown in Table 2. 2-VAP-7 was obtained. Table 2 shows the evaluation results of VAP-2 to VAP-7.

[Example 8]
In the acetalization reaction, a vinyl acetal polymer VAP-8 was obtained in the same manner as in Example 1 except that the amount of butyraldehyde added was changed as shown in Table 2. The evaluation results of VAP-8 are shown in Table 2.

[Comparative Example 1]
A reactor equipped with a stirrer, reflux condenser, argon inlet, and initiator addition port was charged with 700 g of vinyl acetate and 300 g of methanol, and the inside of the system was purged with argon for 30 minutes while bubbling with argon. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.25 g of AIBN was added to initiate polymerization. After polymerization at 60 ° C. for 180 minutes, the polymerization was stopped by cooling. The polymerization rate when the polymerization was stopped was 40%. Subsequently, unreacted monomers were removed while sometimes adding methanol under reduced pressure at 30 ° C. to obtain a methanol solution (concentration 30%) of polyvinyl acetate (PVAc).

  Next, 14.0 g of sodium hydroxide methanol solution (concentration 10.0%) was added to 497 g of PVAc methanol solution prepared by adding methanol thereto (100 g of PVAc in the solution), and the mixture was heated at 40 ° C. Saponification was carried out (the PVAc concentration of the saponification solution was 20% and the molar ratio of sodium hydroxide to vinyl acetate units in PVAc was 0.03). After adding the sodium hydroxide methanol solution, a gelled product was formed in about 1 minute. This was pulverized with a pulverizer and allowed to stand at 40 ° C. for 59 minutes to proceed saponification, and then 500 g of methyl acetate was added. In addition, the remaining alkali was neutralized. After confirming the completion of neutralization using a phenolphthalein indicator, the mixture was filtered to obtain a white solid. To the resulting white solid, 2000 g of methanol was added and heated to reflux for 1 hour. After repeating the above washing operation three times, the white solid obtained by centrifugal dehydration was dried in a vacuum dryer at 40 ° C. for 24 hours to obtain unmodified polyvinyl alcohol PVA-C1. The degree of polymerization was 1700, and the degree of saponification was 98.5 mol%. The physical properties are shown in Table 2. Moreover, except using PVA-C1 instead of PVA-1 and changing the amount of butyraldehyde to be added as shown in Table 2, the vinyl acetal polymer VAP-C1 was obtained in the same manner as in Example 1. It was. The evaluation results of VAP-C1 are shown in Table 2.

[Comparative Example 2]
Non-modified polyvinyl alcohol PVA-C2 was produced in the same manner as in Comparative Example 1 except that the molar ratio of sodium hydroxide to vinyl acetate units was changed as shown in Table 1 and a sodium hydroxide methanol solution was added. did. The physical properties are shown in Table 2. Further, a vinyl acetal polymer VAP-C2 was obtained in the same manner as in Example 1 except that PVA-C2 was used instead of PVA-1 and the amount of butyraldehyde added was changed as shown in Table 2. It was. The evaluation results of VAP-C2 are shown in Table 2.

[Comparative Example 3]
In the acetalization reaction, a vinyl acetal polymer VAP-C3 was obtained in the same manner as in Example 1 except that the amount of butyraldehyde added was changed as shown in Table 2. The evaluation results of VAP-C3 are shown in Table 2.

Claims (3)

Vinyl alcohol units and formula (1):

Look containing a structural unit represented in saponification degree was obtained by acetalizing a hydroxy-group-containing polyvinyl alcohol is 80 to 99.9 mol%, a degree of acetalization of 45 to 90 mol%, vinyl acetal Polymer. The vinyl acetal polymer according to claim 1, obtained by acetalizing a hydroxymethyl group-containing vinyl alcohol polymer in which the content of the structural unit represented by the formula (1) is 0.1 to 30 mol%. The vinyl acetal polymer according to claim 1 or 2 , wherein the degree of acetalization is 80 to 90 mol%.