JP3411264B2 - Method for producing polyvinyl acetal resin - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polyvinyl acetal resin.

[0002]

2. Description of the Related Art Polyvinyl acetal resins have a high affinity for inorganic materials and are widely used for copper foil adhesives for printed circuits, safety glass intermediate films, ceramic binders, etc. due to their properties. As a production method, after the polyvinyl alcohol as a raw material is uniformly dissolved in water, an acid catalyst, an aqueous medium method in which an aldehyde is added to start an acetalization reaction, and a heterogeneous system in which polyvinyl alcohol is dispersed in an organic solvent are acetalized. Typical examples include a solvent method for initiating a reaction and a homogeneous method in which these are combined, but an aqueous medium method, which is said to be the cheapest industrially, is often adopted.

In the aqueous medium method, the water solubility decreases with the progress of the acetalization reaction, so that the polyvinyl acetal resin gradually precipitates. At this time, if the precipitated particles agglomerate, they are formed when the acid catalyst is neutralized. However, there are problems such as insufficient removal of impurities such as alkali metal salts, and difficulty in handling.

In order to suppress such agglomeration of precipitated particles, various reaction conditions have been improved so far, and a method of using a surfactant together has been proposed. For example, JP-A-54
-47795 and Japanese Patent No. 2980947 describe that the acetalization reaction is started while maintaining the temperature at 5 to 12 ° C in the presence of an anionic surfactant such as sodium dodecylbenzenesulfonate and a hydrochloric acid catalyst. JP-A-59-81312 describes that polyvinyl acetal having a uniform particle size is produced in the presence of a special modified nonionic surfactant and a hydrochloric acid catalyst.

However, in the conventional aqueous medium method represented by these known examples, the reaction is basically started in a low temperature region where a hydrochloric acid catalyst which is a strong acid is required and a refrigerator at 20 ° C. or lower is required. Without this, it was impossible to sufficiently prevent the agglomeration and enlargement of the produced particles even if the surfactant was used in combination.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and by combining a specific acid catalyst and a specific surfactant, polyvinyl acetal is less likely to agglomerate produced particles. It is to provide a method for producing a base resin.

[0007]

Means for Solving the Problems That is, the present invention provides a method for producing a polyvinyl acetal resin in an aqueous phase, wherein the acid catalyst (A) and the surfactant (B) used in the acetalization reaction are represented by the following general formula: A method for producing a polyvinyl acetal-based resin, wherein 0.03 ≤ [pH (A) x γ (B)] ≤ 0.20 ... (1) pH (A) ... temperature 25 ° C. PH of the 2% aqueous solution of the acid catalyst (A) in γ (B) ...
Surface tension of aqueous solution (N / m) Furthermore, it is a method for producing a polyvinyl acetal resin, characterized in that the acetalization reaction is carried out while maintaining the system temperature at 20 ° C. or higher.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The production method of the present invention is a process of mixing an aldehyde, an acid catalyst and a surfactant in an aqueous polyvinyl alcohol solution as a raw material and then heating the mixture to accelerate the acetalization reaction and generate particles. Is characterized by the acid catalyst used, the surfactant, and the temperature conditions.

The acid catalyst and the surfactant used in the present invention preferably satisfy the following general formula. 0.03 ≤ [pH (A) x γ (B)] ≤ 0.20 ... (1) pH (A) ... pH of an acid catalyst (A) 2% aqueous solution at a temperature of 25 ° C γ (B) ... temperature 2% of surfactant (B) at 25 ° C
Surface tension of aqueous solution (N / m) where [pH (A) × γ (B)] is the pH (hydrogen ion concentration) of the acid catalyst (A) at a temperature of 25 ° C. and the surfactant (B) at the same temperature. Represents the product of the surface tension and

When [pH (A) × γ (B)] is less than 0.03, the pH of the acid catalyst (A) is too low, so that the effect of the surfactant is reduced and particles tend to aggregate. Not preferable. On the other hand, when [pH (A) x γ (B)] exceeds 0.20, the catalytic effect of acid and the surface-active function of the surfactant are poor, so that the acetalization reaction is delayed and the particles are agglomerated, which is preferable. Absent.

The types of the acid catalyst (A) and the surfactant (B) used in the present invention are not particularly limited as long as they satisfy the above general formula, but the acid catalyst has a pH of 1 at a temperature of 25 ° C. So-called weak acid type exceeding 1.0, for example, phosphoric acid,
Examples thereof include sulfuric acid, acetic acid, citric acid, glyoxylic acid, malic acid, succinic acid and gluconic acid. The surfactant can be widely selected from anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants, and anionic surfactants are particularly preferably used.

The amount of the acid catalyst (A) used in the present invention is preferably 0.1 based on the raw material polyvinyl alcohol resin.
-30% by weight, more preferably 1-15% by weight.

The amount of the surfactant (B) used is preferably 1 to 10 relative to the raw material polyvinyl alcohol resin.
It is 0% by weight, more preferably 1 to 50% by weight.

The reaction temperature during the acetalization reaction according to the production method of the present invention is 20 ° C. or higher, preferably 25 ° C. or higher,
It is particularly preferably 30 ° C or higher. If the reaction temperature is lower than 30 ° C., the progress of the acetalization reaction is slow, and a cooler is required, which is not preferable in terms of cost. The upper limit of the reaction temperature is not particularly limited, but it is 200 for controlling the side reaction.
C. or less, particularly 150.degree. C. or less is preferable.

The raw material polyvinyl alcohol resin used in the present invention is not particularly limited, but among them, vinyl alcohol-vinyl acetate obtained by partially saponifying polyvinyl acetate is preferable. Particularly, a vinyl alcohol-vinyl acetate copolymer having a saponification rate of 80 to 99.5 mol% is preferable. Further, the average degree of polymerization of the vinyl alcohol-vinyl acetate copolymer is preferably 50 to 5,000, particularly preferably 100 to 4,000.

Examples of the aldehyde to be reacted with the polyvinyl alcohol polymer in the present invention include aliphatic aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, pentyl aldehyde, n-hexyl aldehyde, cyclohexyl aldehyde and octyl aldehyde. And aromatic aldehydes such as benzaldehyde, benzyl aldehyde and naphthyl aldehyde can be used.

In the present invention, in addition to the above-mentioned aldehydes, it is also possible to use glyoxylic acid having a functional group, ketones such as diacetone alcohol and the like.

After the acetalization reaction, the acid catalyst is neutralized with sodium hydroxide or the like, filtered, washed and dried to obtain a dry powder.

According to the present invention, the particle size suitable for workability is
In addition, a polyvinyl acetal resin having good properties such as solubility and adhesiveness can be manufactured.

[0020]

EXAMPLES The present invention will be described below with reference to examples.
Unless otherwise specified, "parts" and "%" represent parts by weight and% by weight, respectively. (Example 1) 40 ion-exchanged water was placed in a container equipped with a stirrer.
0 parts of polyvinyl alcohol resin (degree of polymerization 17
00, vinyl alcohol part 98.0%, vinyl acetate part 2.0%) 100 parts with stirring. Then, the internal temperature was raised from room temperature to 90 ° C., and the polyvinyl alcohol resin was dissolved over 2 hours while maintaining the temperature at 90 ° C. After cooling this aqueous solution to 50 ° C, industrial glyoxylic acid [40% concentration, manufactured by Nippon Synthetic Chemical Industry, 2% as an acid catalyst]
Aqueous solution pH (25 ° C.) = 2.0] 25 parts, as a surfactant disodium dodecyl diphenyl ether disulfonate [trade name: Newcol 271A (active ingredient 47
%), Made by Nippon Emulsifier, 2% aqueous solution surface tension (25 ° C.) =
0.0341 N / m] was added to 10.6 parts, and the mixture was mixed at 50 ° C. for 3 minutes.
Mix for 0 minutes. Next, 53 parts of butyraldehyde was added dropwise while maintaining the internal temperature at 50 ° C., and the mixture was stirred for 3 hours, whereupon a white polyvinyl butyral resin powder was deposited. After cooling to room temperature, neutralize with sodium hydrogen carbonate,
The produced resin was filtered, washed with water and dried to obtain a granular polyvinyl acetal resin. In addition, in this reaction [p
The value of H (A) × γ (B)] was 0.0682.

Analysis of the obtained polyvinyl acetal resin showed that the vinyl alcohol unit was 21.0%, the vinyl acetate unit was 1.5%, and the vinyl butyral unit was 7%.
It was 7.5% and the average particle diameter was 250 μm. Furthermore, 5% in ethanol / toluene equivalent mixed solvent
The solution viscosity of the resin concentration was 55 mPa · s (20 ° C.), and the transparency of the solution was 40 cm or more.

The compositional analysis of the polyvinyl acetal resin is 1H-NMR, and the average particle size is standard sieve (JIS Z).
8801), the solution viscosity is a B-type viscometer,
Solution clarity was measured by the Nessler tube method (JIS K 6728). The pH of a 2% aqueous solution of the acid catalyst at a temperature of 25 ° C was measured with a glass electrode type hydrogen ion densitometer (HM-5ES manufactured by Toa Denpa Kogyo KK), and the temperature of a 2% aqueous solution of the surfactant was 25 ° C. Surface tension is Kyowa CBV
It was measured with a P-type surface tensiometer (manufactured by Kyowa Kagaku Co., Ltd.).

(Example 2, Comparative Examples 1 and 2) A polyvinyl acetal resin was produced in the same manner as in Example 1 except that the kinds of the acid catalyst and the surfactant and the reaction temperature were changed, and the characteristics were evaluated. It was The production conditions are shown in Table 1, and the physical property evaluation results are shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

EFFECTS OF THE INVENTION The polyvinyl acetal resin obtained by the production method of the present invention is not a fine powder but a granular powder, so that it is excellent in handleability during dissolution work and the transparency of the solution. Has good characteristics.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A 61-81450 (JP, A) JP-A 60-42402 (JP, A) JP-A 10-60046 (JP, A) JP-A 6- 239929 (JP, A) JP 59-117505 (JP, A) JP 2000-297117 (JP, A) JP 6-211918 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) C08F 8/00-8/50

Claims (2)

(57) [Claims] 1. A method for producing a polyvinyl acetal resin in an aqueous phase, wherein the acid catalyst (A) and the surfactant (B) used in the acetalization reaction satisfy the following general formula. -Based resin manufacturing method 0.03 ≤ [pH (A) x γ (B)] ≤ 0.20 .... (1) pH (A) ... pH γ of 2% aqueous solution of acid catalyst (A) at a temperature of 25 ° C (B) ... Surfactant (B) 2% at a temperature of 25 ° C.
Surface tension of aqueous solution (N / m) 2. The method for producing a polyvinyl acetal resin according to claim 1, wherein the acetalization reaction is carried out while maintaining the system temperature at 20 ° C. or higher.