JP2008260914A - Polyvinyl alcohol resin composition and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PVA resin composition in which hydrotalcite particles are finely dispersed without aggregation of the hydrotalcite particles even at high concentration; and to provide a method of manufacturing the composition. <P>SOLUTION: A vinylester resin solution is saponified at a saponification degree ranging from 65 mol% to 100 mol% in the presence of hydrotalcite. The PVA resin composition in which the hydrotalcite particles, of which 90% or higher have particle diameters of 600 nm or smaller, are finely dispersed, can be obtained by mixing hydrotalcite in a phase of manufacturing the PVA resin, even if the PVA resin composition contains hydrotalcite at a high concentration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a polyvinyl alcohol resin composition in which hydrotalcite is finely dispersed in polyvinyl alcohol resin particles and a polyvinyl alcohol resin composition obtained by the production method.

  In some cases, ester groups such as acetyl groups possessed by vinyl ester resins such as EVOH resins and PVA resins are separated during production and processing to generate carboxylic acid (acetic acid). Carboxylic acid generated during molding and processing causes deterioration of the environment at the production site, and when it is melt-molded under acidic conditions, ketalization or acetalization occurs between the molecular chains of vinyl alcohol resin. The reaction that causes gelation proceeds, etc., may cause deterioration of the vinyl ester resin, or cause odors, coloring, fish eyes, etc. in various molded articles and films of the vinyl ester resin. It is known that the quality of molded articles and packages will be reduced. Hydrotalcite is widely used as a compounding agent for solving such problems in vinyl ester resins.

  Here, as a method for producing a PVA resin composition formed by blending hydrotalcite, as described in paragraph 9 of JP-A-6-166786, (a) PVA and hydrotalcite are mixed in a powder state. (B) a method in which both are melt-kneaded into pellets, (c) a method in which hydrotalcite is made into an aqueous dispersion and sprayed onto PVA powder or pellets.

  Hydrotalcite particles have a layered structure and have the property that particles tend to aggregate. Even if they are subdivided by delamination, these particles are aggregated again in the resin. Often exists. However, in order to enhance the blending effect of hydrotalcite, it is preferable to uniformly disperse hydrotalcite particles having a small average particle diameter, in other words, in a state where the surface area is large. The state where the surface area is large means a state where the above-mentioned particles are dispersed apart from each other, and a state where the layer forming the particles is peeled off and the particles themselves become small.

  For example, in the above method (a) (method of mixing PVA resin and hydrotalcite in a powder state), hydrotalcite cannot be uniformly dispersed due to the difference in specific gravity between PVA and hydrotalcite. Again, many of the hydrotalcite particles mixed together in an aggregated state are included. Also, in the method (b) in which the PVA resin and hydrotalcite are melt-kneaded into pellets, not only the effect of dispersing hydrotalcite particles is weak, but also the particles tend to aggregate, The talcite may become a lump. Further, as the saponification degree becomes higher, the melting temperature has to be increased, and this causes a new problem that decomposition of PVA occurs. Therefore, a mixing method in the case of a PVA resin having a high saponification degree Is not appropriate. Furthermore, in the method (c), the hydrotalcite is simply attached to the surface of the PVA powder, and the hydrotalcite is not dispersed in the PVA.

JP-A-6-166786

  The present invention has been made in view of the circumstances as described above, and an object of the present invention is to make a finely dispersed PVA resin composition and a method for producing the same even if the hydrotalcite particles do not aggregate and have a high concentration. Is to provide.

The present invention has found that by mixing hydrotalcite at the production stage of the PVA resin, a finely dispersed PVA resin composition can be obtained even if the hydrotalcite is in a high concentration in the PVA resin particles, The present invention has been completed.
That is, the method for producing a PVA resin composition of the present invention is characterized in that a vinyl ester resin solution is saponified in the presence of hydrotalcite in a range of saponification degree of more than 65 mol% to 100 mol%. To do.

  The PVA-based resin composition of the present invention is a resin composition in which hydrotalcite is dispersed in polyvinyl alcohol-based resin particles having a saponification degree of more than 65 mol% to 100 mol%. % Or more of particles having a particle size of 600 nm or less.

  Such a PVA-type resin composition can be used suitably as a compounding agent of a thermoplastic resin.

  According to the production method of the present invention, hydrotalcite particles can be saponified in a uniformly dispersed state without aggregation of hydrotalcite particles, and a PVA resin can be produced. Even if it is made to contain, the PVA-type resin composition of this invention in which 90% or more of the said hydrotalcite particle | grains are disperse | distributed with a particle size of 600 nm or less can be obtained.

[Production method of PVA resin composition]
First, the manufacturing method of the PVA-type resin of this invention is demonstrated.
The method for producing a PVA resin of the present invention is characterized by saponifying a vinyl ester resin solution in the presence of hydrotalcite.

  The vinyl ester resin solution used in the present invention is a solution in which a vinyl ester resin capable of producing a PVA resin by saponification is dissolved in a solvent. Accordingly, the monomer constituting the vinyl ester resin is appropriately selected according to the constituent monomer of the PVA resin to be obtained. Specific examples of vinyl ester monomers that can be used include vinyl formate, vinyl acetate, and propion. Vinyl acid vinyl, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate, etc. Of these, vinyl acetate is preferably used It is done.

  As long as the object of the present invention is not impaired, an unsaturated monomer other than the vinyl ester monomer may be included as a copolymerizable component. Examples of the unsaturated monomer include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-olefins such as α-octadecene; acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride , Unsaturated acids such as itaconic acid or salts thereof, mono- or dialkyl esters, etc .; nitriles such as acrylonitrile and methacrylonitrile; amides such as diacetone acrylamide, acrylamide and methacrylamide; ethylene sulfonic acid, allyl sulfonic acid, methallyl Olefin sulfonic acids such as sulfonic acids or salts thereof; alkyl vinyl ethers; dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxyp Polyoxyalkylene (meth) allyl ether such as pyrene (meth) allyl ether, polyoxyalkylene (meth) acrylate such as polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylamide, Polyoxyalkylene (meth) acrylamide such as polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene Examples include allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

  Further, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidopropyltrimethylammonium chloride, 2-acryloxyethyltrimethylammonium chloride, 2-methacryloxyethyltrimethylammonium chloride, 2-hydroxy-3- Cationic group-containing monomers such as methacryloyloxypropyltrimethylammonium chloride, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, 3-butenetrimethylammonium chloride, dimethyldiallylammonium chloride, diethyldiallylammonium chloride, acetoacetyl group-containing monomers , Isopropenyl acetate, 1-methoxy It may be copolymerized vinyl acetate and the like.

  Furthermore, dihydroxyalkenes such as 3,4-dihydroxy-1-butene, 4,5-dihydroxy-1-pentene, 5,6-dihydroxy-1-hexene, and 4,5-dihydroxy-3-methyl-1-pentene Hydroxyacylalkenes such as 3-acyloxy-4-hydroxy-1-butene and 4-acyloxy-3-hydroxy1-butene; 3,4-diacyloxy-1-butene, 3,4-diacyloxy-2-methyl-1 -Diacyloxyalkenes such as butene, 4,5-diacyloxy-1-pentene, 4,5-acyloxy-3-methyl-1-pentene, 5,6-diacyloxy-1-hexene; glycerin monoallyl ether, glycerin mono Glycerin monounsaturated alkyl ethers such as vinyl ether and glycerin monoisopropenyl ether; , 3-diacetoxy-1-allyloxypropane, acetoxy group-containing allyloxypropanes such as 2-acetoxy-1-allyloxy-3-hydroxypropane, 3-acetoxy-1-allyloxy-2-hydroxypropane; vinyl ethylene carbonate, etc. Acetal group-containing vinyl compounds such as 2,2-dimethyl-4-vinyl-1,3-dioxolane can also be copolymerized.

  Polymerization of the vinyl ester monomers as described above, and copolymerization with other unsaturated monomers blended as necessary are known methods such as bulk polymerization, solution polymerization, suspension polymerization, dispersion polymerization, or emulsion polymerization. However, solution polymerization is preferably performed. The method for charging the monomer component at the time of polymerization is not particularly limited, and any method such as batch charging, divided charging, continuous charging, etc. may be employed.

  In the case of solution polymerization, preferred examples of the solvent include lower alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propanol and butanol, and ketones such as acetone and methyl ethyl ketone. Examples of the polymerization catalyst include known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide and lauryl peroxide, and low-temperature active radical polymerization such as azobisdimethylvaleronitrile and azobismethoxydimethylvaleronitrile. A catalyst etc. are mentioned, The usage-amount of a polymerization catalyst is suitably determined according to the kind of catalyst, and a polymerization rate.

  The degree of polymerization of the vinyl ester resin may be adjusted according to the degree of polymerization of the PVA resin to be finally obtained. Although there is no particular limitation, the polymerization degree of the PVA resin to be obtained is usually 100 to 4000 (more preferably 150 to 3000, more preferably 200 to 2600) as the polymerization degree measured according to JIS K6726. The degree of polymerization of the vinyl ester resin as a raw material is preferably adjusted within the above range. When the degree of polymerization becomes too high, hydrotalcite tends to be hardly taken into the saponified product.

  The vinyl ester resin solution obtained by polymerization is usually a solution of a solvent at the time of polymerization, but the solvent at the time of polymerization may be replaced with another solvent. Such a solvent is not particularly limited as long as it can dissolve the vinyl ester resin, and lower alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propanol, and butanol are preferably used, and more preferably methanol is used. Used. The vinyl ester resin obtained by polymerization may be dissolved in the solvent and the concentration may be adjusted for saponification, or when a vinyl ester resin solution is obtained by solution polymerization using a lower alcohol as a solvent. The concentration may be adjusted by adding additional solvents as appropriate, and then subjected to saponification. Prior to saponification, it is preferable to remove unreacted monomers in the solution out of the system.

  Saponification can be initiated by adding a saponification catalyst to the vinyl ester resin solution. Catalysts used for saponification include alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate and lithium methylate; sulfuric acid, Examples include acid catalysts such as hydrochloric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resin. About the usage-amount of this saponification catalyst, it selects suitably by the saponification method, the target saponification degree, etc. Although the reaction temperature of a saponification reaction is not specifically limited, Usually, it is 10-60 degreeC, More preferably, it is 20-50 degreeC.

  In the production method of the present invention, saponification needs to be performed in the presence of hydrotalcite. The hydrotalcite can be blended before the saponification catalyst is blended, simultaneously with the saponification catalyst, after the saponification catalyst is blended, or in the initial stage of the saponification reaction.

Here, hydrotalcite is a name of a natural mineral represented by the chemical formula Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O, but recently, a structure that is basically similar to the above natural mineral is used. It is generally used as a general term for the double hydroxides represented by the following general formula.
^{_{[M 2+ 1-x M 3+ x}} (OH) 2 ] _{(A x / n · mH 2} O)
In the formula, M ²⁺ represents a divalent metal ion such as Mg, Fe, Zn, Ca, Cu, and Co, preferably Mg, Zn, or Ca, and more preferably Mg. M ³⁺ represents a trivalent metal ion such as Al, Ce, Fe, Mn, In, or Cr, preferably Al or Ce, and more preferably Al. x is a number from 0.2 to 0.33, and m is a real number larger than 0, and varies depending on the degree of dehydration, but is generally an integer from 0 to 2. A is carbonate ion (CO ₃ ²⁻ ), HPO ₃ ²⁻ , saturated aliphatic monocarboxylic acid, and preferably carbonate ion. N is the valence of A.

Particularly preferred combinations are hydrotalcites represented by the following general formula.
Mg _1-x Al _x (OH) ₂ (CO ₃ ) _{x / 2} · mH ₂ O
Examples of those in which A is a saturated aliphatic monocarboxylate ion include hydrotalcites disclosed in JP-A-2006-274385. Such hydrotalcites are obtained by ion-exchange of hydrotalcite encapsulating carbonate ions in a saturated aliphatic monocarboxylate aqueous solution, and are preferably used because of having good delamination properties. .

The hydrotalcite in the present invention is a hydrotalcite as described above. Hydrotalcites such as described above, the anion portion of the M ²⁺ (OH) ₂ of M ²⁺ is a positive charge octahedron layer as a host layer caused by substituted by M ^3+, to compensate for this positive charge The guest layer made of interlayer water has a layered structure in which the host layer is alternately stacked.

  The hydrotalcite used in the present invention may be subjected to a surface treatment such as stearic acid, but from the viewpoint of fine dispersion with a vinyl ester resin such as a PVA resin, a surface treatment such as stearic acid is used. Hydrotalcite that has not been used is preferably used.

  Hydrotalcite uses a powder having an average particle size of about 400 to 600 nm. In the powder state, the particles are aggregated to form aggregated particles, but can be used while containing the aggregated particles. Hydrotalcite may be directly blended into the vinyl ester resin solution as a powder, or an alcohol dispersion in which hydrotalcite is dispersed in alcohol may be prepared in advance, and this dispersion may be blended and mixed. Good.

  The blending amount of hydrotalcite is selected according to the amount of hydrotalcite desired to be contained in the PVA resin composition to be finally obtained. The amount of hydrotalcite to be contained in the PVA resin to be finally obtained is usually 0.01 to 100 parts by mass with respect to 100 parts by mass of the PVA resin (more preferably 0.1 to 60 parts). Therefore, it is preferable to blend hydrotalcite in an amount in the above range with respect to the vinyl ester resin.

  Saponification is carried out until the saponification degree exceeds 65 mol%. Preferably it is 68-99 mol%, More preferably, it is 70-98 mol%. This is because if the degree of saponification is too low, physical properties as a PVA-based resin are hardly exhibited, and solid-liquid separation after saponification (separation between saponification solvent and saponification product) becomes difficult.

  A suspension in which the PVA-based resin composition that has become particulate by saponification is dispersed in a solvent is obtained. Therefore, what is necessary is just to obtain a PVA-type resin composition by filtration. The filtration method is not particularly limited, and examples thereof include centrifugation. Moreover, you may neutralize a solvent before filtration. The obtained PVA-based resin composition is washed and dried as necessary. Washing is preferably performed with the aforementioned lower alcohol.

  After saponification, the OH group in the PVA-based resin may be modified by a known post-modification treatment such as urethanization, acetalization, cyanoethylation, oxyalkyleneation, acetoacetylation or the like, if desired.

  According to the manufacturing method as described above, since hydrotalcite is blended in the solution, the aggregated particles are also dispersed and can be uniformly dispersed in the particle state without agglomeration. Furthermore, delamination of hydrotalcite particles in a layered structure occurs in the solution, and the proportion of particles having a particle size of 450 nm or less smaller than the original hydrotalcite particles can also be increased. And since hydrotalcite exists during saponification reaction, the particle | grains of hydrotalcite can be taken in uniformly in the PVA-type resin particle to produce | generate.

[PVA resin composition]
The PVA resin composition of the present invention is manufactured by the above-described manufacturing method of the present invention. Specifically, hydrotalum is contained in polyvinyl alcohol resin particles having a saponification degree of more than 65 mol% to 100 mol%. In the resin composition in which the sites are dispersed, 90% or more of the hydrotalcite particles are dispersed in a particle size of 600 nm or less.

  The PVA resin contained in the PVA resin composition of the present invention is a polymer obtained by saponifying a vinyl ester resin obtained by polymerization of a vinyl ester monomer by the production method of the present invention. Therefore, the monomer which comprises the said PVA-type resin is the above-mentioned vinyl ester-type monomer or its saponification thing, and the other unsaturated monomer contained depending on necessity. Further, by post-modification, the OH group of the PVA-based resin may be appropriately modified by a known post-modification treatment such as urethanization, acetalization, cyanoethylation, oxyalkylenation, acetoacetylation or the like.

  The degree of saponification of the PVA-based resin is more than 65 mol% to 100 mol% (preferably 68 to 99 mol%, more preferably 70 to 98 mol%). The degree of saponification can be appropriately selected depending on the use of the PVA resin composition. In any case, since the characteristics can be exhibited as PVA, the PVA resin composition of the present invention exhibits water solubility.

  Moreover, it is preferable that the average degree of polymerization (measured based on JIS K6726) of the said PVA-type resin is 100-4000, More preferably, it is 150-3000, More preferably, it is 200-2600. If the polymerization degree is too low, it is difficult to obtain a powder of the PVA resin composition by solid-liquid separation after the production of the PVA resin composition. If the polymerization degree is too high, the hydrotalcite becomes PVA resin particles. Difficult to disperse inside.

  The average particle size (measurement of JIS Z 8801) of the PVA-based resin composition powder of the present invention varies depending on the type of PVA-based resin and the production method (saponification conditions, etc.), but is usually 5.0 to 0.01 mm. is there. Hydrotalcite is dispersed in the PVA resin particles constituting the powder. This hydrotalcite is dispersed in a particle state in which 90% or more of the particles have a particle size of 600 nm or less, preferably 500 nm or less, particularly preferably 450 nm or less. The proportion of hydrotalcite particles having a particle size of 800 nm or more is preferably 5% or less. In addition, the particle size of a hydrotalcite here is the value observed and measured with the scanning electron microscope (SEM), after cutting a PVA-type resin composition with a microtome.

  In the PVA-type resin composition of this invention, it can be made to contain in the range of 0.01-100 mass parts of hydrotalcite with respect to 100 mass parts of PVA-type resin. Therefore, what is necessary is just to select a hydrotalcite content rate suitably in the said range according to the use of a PVA-type resin composition. From the viewpoint of uniform dispersion, the content of hydrotalcite in the PVA-based resin composition is preferably 0.1 to 60 parts by mass, more preferably 0.8 to 100 parts by mass of the PVA-based resin. 5 to 40 parts by mass.

  The PVA resin composition of the present invention can itself be used for molding as PVA pellets, and can be appropriately blended in a thermoplastic resin such as a polyolefin resin as a compounding agent. For thermoplastic resins such as polyolefin resins, hydrotalcite may be used as a compounding agent from the viewpoint of preventing deterioration of the quality of molded products due to unreacted monomers and their decomposition products, and long run properties during melt molding. . However, when a thermoplastic resin and hydrotalcite are melt-mixed, it is difficult to disperse in a state where a large surface area can be secured because the hydrotalcite easily aggregates, so that a sufficient hydrotalcite adsorption effect can be obtained. It is. In this regard, when the PVA resin composition of the present invention is blended with other resins such as a thermoplastic resin as a compounding agent, aggregation of hydrotalcite particles is suppressed by the intervention of PVA, and in the thermoplastic resin It can be uniformly dispersed. Therefore, by using the PVA resin composition of the present invention, it is dispersed in a thermoplastic resin composition in a particle state with a particle size of 600 nm or less, which is difficult to mix with a normal hydrotalcite single method, without aggregation. In addition, hydrotalcite particles in a finer state can also be included due to delamination of particles, which can efficiently remove unreacted monomers and their decomposition products, carboxylic acid odor generated from PVA resin, etc. Adsorbs and removes well. Moreover, even when using the polyvinyl alcohol-type resin composition of this invention as a masterbatch, the favorable dispersibility of a hydrotalcite can be maintained and the same effect is acquired.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
In the following examples, “parts” and “%” mean mass basis unless otherwise noted. The degree of saponification is a value obtained from the alkali consumption required for hydrolysis of the residual vinyl acetate structural unit of the polyvinyl alcohol resin minus the amount of hydrotalcite, and the degree of polymerization is measured based on JIS K6726. It is the value.

[Example 1]
Into a reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer, 1200 parts of vinyl acetate, 192 parts of methanol, and 0.06 mol% of azobisisobutyronitrile (compared with vinyl acetate) were added, and nitrogen was stirred. Polymerization was started by raising the temperature under an air stream.
When the polymerization rate of vinyl acetate reached 73%, m-dinitrobenzene and methanol for dilution / cooling were added to complete the polymerization. Subsequently, unreacted vinyl acetate monomer was removed out of the system by a method of blowing methanol vapor to obtain a methanol solution of polyvinyl acetate.
This methanol solution of polyvinyl acetate was further diluted with methanol to adjust the concentration to 32%. Charge 500 parts of this diluted solution to a kneader, add 9.7 parts of hydrotalcite (average particle size 500 nm) and mix, then keep the solution temperature at 35 ° C and stir while stirring with a 2% methanol solution of sodium hydroxide. And 2.5 mmol with respect to 1 mol of vinyl acetate. As saponification progressed, saponification product (PVA resin) was precipitated and finally became particulate. The resulting polyvinyl alcohol resin composition was neutralized with acetic acid, filtered, washed well with methanol and dried in a hot air dryer to obtain a PVA resin composition powder having an average particle size of 460 μm.

  The obtained PVA-based resin had a saponification degree of 80.0 mol% and a polymerization degree of 2100. Moreover, 10 parts of hydrosartite was contained with respect to 100 parts of PVA-type resin in PVA resin composition particle | grains. Further, when the particle size of hydrosartite in the resin composition particles was observed and measured by SEM (JSM-6060LA manufactured by JEOL Ltd.), it was found that 90% or more of the particles had a particle size of 450 nm or less. It could be confirmed. Further, hydrotalcite particles having a particle size of 800 nm or more were not recognized.

[Comparative Example 1]
A PVA-based resin powder (average particle size of 440 μm) was obtained in the same manner as in Example 1 except that no hydrosartite was added.
An attempt was made to knead 100 parts of the obtained PVA-based resin powder (particle size: 440 μm) and 10 parts of hydrotalcite of the same type used in Example 1 at 200 ° C. with a Brabender. The torque was over and hydrotalcite could not be sufficiently dispersed.

  The PVA resin composition of the present invention can be used alone as a molding raw material, and can also be used as a compounding agent for improving the properties of other thermoplastic resins. According to the method for producing a PVA-based resin composition of the present invention, it is possible to obtain a PVA-based resin composition in which hydrotalcite is well dispersed without agglomeration without melting and kneading at a high temperature.

Claims (5)

A method for producing a polyvinyl alcohol-based resin, comprising saponifying a vinyl ester-based resin solution in the presence of hydrotalcite within a saponification degree ranging from 65 mol% to 100 mol%. The method for producing a polyvinyl alcohol resin according to claim 1, wherein a solvent of the polyvinyl ester resin solution is a lower alcohol having 1 to 4 carbon atoms. In a resin composition in which hydrotalcite is dispersed in polyvinyl alcohol-based resin particles having a saponification degree of more than 65 mol% to 100 mol%,
A polyvinyl alcohol-based resin composition in which 90% or more of the hydrotalcite is dispersed with a particle size of 600 nm or less. The polyvinyl alcohol resin composition according to claim 3, wherein the hydrotalcite is contained in an amount of 0.01 to 100 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol resin. The compounding agent for thermoplastic resins containing the polyvinyl alcohol-type resin composition of Claim 3 or 4.