JP2803874B2 - Melt molding method of water-soluble vinyl alcohol polymer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for melt-molding a water-soluble vinyl alcohol copolymer containing a vinyl alcohol unit (A), a vinyl ester unit (B) and an oxyalkylene allyl ether unit (C). How to do it.

2. Description of the Related Art A molded product of polyvinyl alcohol, for example, a film has excellent properties such as fragrance retention, transparency, oil resistance, antistatic properties, oxygen barrier properties, heat retention properties, and hydrophilicity, water solubility or water solubility. Since it has dispersibility, it can be used for applications that are not suitable for ordinary hydrophobic polymer films.

As a method for obtaining a film from polyvinyl alcohol, a method in which the polymer is dissolved in water and cast is usually employed. In this case, the obtained film is flexible under the high humidity condition, but has a property that the flexibility is impaired under the low humidity condition. Incorporation of a plasticizer is performed.

As a method of obtaining a film or other molded product from polyvinyl alcohol, a method of melt-extruding the polymer in a water-containing state is also known. Also in this case, in order to maintain the flexibility of the obtained molded product, a plasticizer is used in combination.

Attempts have been made to melt extrude polyvinyl alcohol under substantially anhydrous conditions.However, polyvinyl alcohol has a high softening point and its softening point is close to the thermal decomposition temperature. Have difficulty. Thus, when polyvinyl alcohol is melt-molded, a large amount of a plasticizer such as glycerin is blended and subjected to extrusion molding.

In addition, injection molding of polyvinyl alcohol is not generally performed.

Polyvinyl alcohol, after polymerizing vinyl acetate,
Although produced by saponification, a "copolymerized" polyvinyl alcohol can be obtained by using a comonomer in combination during polymerization. Further, the polyvinyl alcohol can be "post-modified" by reacting another compound with the OH group of the polyvinyl alcohol. These modified polyvinyl alcohols essentially have the properties of polyvinyl alcohol as described above, but also have properties based on the introduced modified groups.

As one of such modified polyvinyl alcohols,
Vinyl alcohol polymers into which oxyalkylene units have been introduced are known, and for example, the following various foreign and domestic applications have been filed.

For example, U.S. Patent Nos. 1971662, 2844570, and 2990398 disclose oxyethylene group-containing polyvinyl alcohol obtained by adding ethylene oxide to polyvinyl alcohol.

U.S. Pat. Nos. 3,033,481 and 4,369,281 show oxyalkylene group-containing polyvinyl alcohol obtained by saponifying a polymer obtained by graft-polymerizing vinyl acetate in the presence of polyalkylene glycol.

U.S. Pat. Nos. 4,618,648 and 4,675,360 show copolymers of vinyl alcohol and poly (alkyleneoxy) acrylates, which can be injection molded and extruded. It has also been shown that the resulting molded article has water solubility and flexibility.

JP-A-59-155408 discloses a modified polyvinyl alcohol obtained by saponifying a copolymer of an unsaturated monomer having an oxyalkylene group and vinyl acetate. In this publication, various types of uses are listed, and a molded product is also mentioned as an example of the use, but the molding method is not disclosed.

JP-A-1-158016 discloses a water-resistant flexible film comprising an oxyalkylene group-containing vinyl alcohol polymer film. The publication states that "methods for film formation include a method of casting an aqueous solution of the polymer, a method of heating and extruding under water-containing conditions, and a method of melt extrusion." This is a method related to the drawing method, and the melt extrusion method (also the method of heating and extruding under water-containing conditions) is described only in a word.

Problems to be Solved by the Invention The method of forming polyvinyl alcohol by the casting method requires melt-extrusion, such as the necessity of adjusting the aqueous solution, the slow film formation speed, and the long drying time after film formation. There are various disadvantages compared to the law. When a plasticizer is used in combination to impart flexibility to a molded product, there is a similar disadvantage, and a new problem of bleeding caused by the blended plasticizer arises.

The method of melt-extruding polyvinyl alcohol in a water-containing state also has a disadvantage that drying after molding takes a long time. When a plasticizer is used in combination to impart flexibility to a molded product, there is the same disadvantage as described above, and a new problem of bleeding caused by the blended plasticizer arises.

The method of blending a large amount of plasticizer with polyvinyl alcohol and extruding it may cause the blended plasticizer to bleed on the surface of the molded product and cause stickiness, or cause poor adhesion when laminated with other base materials. There is.

In this regard, the vinyl alcohol-based polymer into which the oxyalkylene unit has been introduced has an advantage in that the blending of the plasticizer can be omitted because the vinyl alcohol-based polymer itself has flexibility.

However, the above-mentioned U.S. Pat.
844570, the oxyethylene group-containing polyvinyl alcohol described in the specification of 2990398, it is difficult to adjust the length of the oxyethylene group that is a side chain, it is said that the productivity is inferior because it becomes secondary processing There is a disadvantage.

U.S. Pat.No. 3,038,381, oxyalkylene group-containing polyvinyl alcohol described in 4,369,281,
In the production thereof, the reactivity at the time of graft polymerization to the alkylene glycol is low, and it is difficult to say that it is practical.

The vinyl alcohol / poly (alkyleneoxy) acrylate copolymers described in US Pat. Nos. 4,618,648 and 4,675,360 saponify after copolymerizing vinyl acetate and poly (alkyleneoxy) acrylate. However, since the oxyalkylene group is easily eliminated during the saponification reaction, the product after saponification is actually a mixture with the eliminated alkylene glycol or polyalkylene glycol.

JP-A-59-155408 only discloses production and expected uses of an oxyalkylene group-containing vinyl alcohol polymer, and does not disclose any other molding methods as well as melt molding. .

Japanese Patent Application Laid-Open No. 1-158016 suggests melt molding of a vinyl alcohol polymer having an oxyalkylene group, but if melt molding is actually attempted, smooth melt molding is not easy.

Under such a background, the present invention has been made to provide an industrially applicable method for melt-molding an oxyalkylene group-containing vinyl alcohol copolymer under substantially anhydrous conditions. is there.

Means for Solving the Problems The melt molding method of the water-soluble vinyl alcohol polymer of the present invention is represented by the following formula: Wherein each of the vinyl alcohol unit (A), the vinyl ester unit (B) and the oxyalkylene allyl ether unit (C) contains a mol%, b mol%, and c mol%, and R ¹ in (B) is an alkyl group; R ² and R ³ in (C) are H or an alkyl group, R ⁴ in (C) is H,
An alkyl group, a phenyl group or a substituted phenyl group, wherein n is 1 to 300, and all of the following relationships are satisfied: 0.1 ≦ c ≦ 20, 50 ≦ 100a / (a + b) ≦ 100, and temperature 210 ° C., load An oxyalkylene group-containing vinyl alcohol copolymer having a melt index at 2160 g of 5 g / 10 min or more is melt-molded under substantially anhydrous conditions.

 Hereinafter, the present invention will be described in detail.

The oxyalkylene group-containing vinyl alcohol copolymer used in the present invention comprises a vinyl alcohol unit (A), a vinyl ester unit (B) and an oxyalkylene allyl ether unit (C) in a mol%, b mol%, and c mol%, respectively. Including. Here, R ¹ in (B) is an alkyl group (especially a methyl group), R ² and R ³ in (C) are H or an alkyl group (especially both R ² and R ³ are H, one of the other is a methyl group H), R ⁴ is H, an alkyl group, a phenyl group or substituted phenyl group in (C), n is 1 to 30
0 (especially 3 to 50). A typical example of the vinyl ester unit (B) is vinyl acetate, and a typical example of the oxyalkylene allyl ether unit (C) is polyoxyethylene allyl ether, polyoxyethylene methallyl ether,
Polyoxypropylene allyl ether and polyoxypropylene methallyl ether.

 First, the copolymer is required to satisfy the following relationships: 0.1 ≦ c ≦ 20, 50 ≦ 100a / (a + b) ≦ 100.

The first formula shows that the proportion of oxyalkylene allyl ether units (C) in the copolymer is 0.1 to 20 mol%. When the proportion of the unit (C) is less than 0.1 mol%, the modifying effect is insufficient, and when it exceeds 20 mol%, the intrinsic properties of the vinyl alcohol copolymer are impaired.
A particularly preferred range is from 0.1 to 5 mol%.

The second equation means that the saponification degree of the vinyl ester component before saponification is 50 to 100 mol%. If the saponification degree is less than 50 mol%, the vinyl alcohol group has fresh water, fragrance retention, oil resistance, antistatic properties, oxygen barrier properties,
Properties such as heat retention cannot be sufficiently obtained. A particularly preferred range is 80 to 100 mol%.

If necessary, monomer units other than (A), (B) and (C) may contain about 30 mol% or less. Examples of such units include α-olefins (ethylene, propylene). , Long-chain α-olefins, etc.) and ethylenically unsaturated carboxylic acid monomers (acrylate, methacrylate, acrylonitrile, methacrylonitrile, vinyl chloride, vinyl ether, etc.).

For the above copolymer, it is useful to use vinyl acetate as the unit (B). Moreover, this case, the proportion of total resin oxyalkylene units CHR ² -CHR ³ -O _n in a unit (C) is at 3 to 40% by weight, more effect is remarkable. That is, focusing on the oxyalkylene unit, the molar ratio of (C) in the copolymer is 0.1%.
Not only 1 to 20 mol% (preferably 0.1 to 5 mol%), but also the weight ratio of the oxyalkylene unit in (C) is 3 to 40% by weight (preferably 5 to 40% by weight) of the whole resin.
Is required. This indicates that the degree of localization-delocalization of the oxyalkylene unit and the length of the oxyalkylene unit in the copolymer are limited in order to perform smooth melt molding under anhydrous conditions. And n
And the degree of saponification is 80 to 100 mol%, which is a high practical range.

Furthermore, the oxyalkylene group-containing vinyl alcohol copolymer used in the present invention is required to have a melt index of 5 g / 10 min or more at a temperature of 210 ° C. and a load of 2160 g. If this value is less than 5 g / 10 min, it is difficult to perform smooth melt molding even if other conditions are satisfied. Here, the melt index is measured using a melt indexer manufactured by Toyo Seiki Seisakusho with a nozzle of 1 mmφ × 10 mm.

As described above, in the present invention, melt molding under substantially anhydrous conditions can be industrially performed only when the oxyalkylene group-containing vinyl alcohol copolymer satisfying the above conditions is used.

The oxyalkylene group-containing vinyl alcohol copolymer is obtained by polymerizing the monomers constituting the vinyl ester unit (B) and the oxyalkylene allyl ether unit (C) together with other copolymerizable monomers, if necessary. It is manufactured by doing. Most or all of the vinyl ester units (B) are converted to vinyl alcohol units by saponification.

As a polymerization method, a solution polymerization method is usually employed, and a suspension polymerization method, an emulsion polymerization method, or the like may be employed depending on the case.

As the saponification reaction, an alkali saponification method, an acid saponification method, or the like is employed.

The melt molding of the oxyalkylene group-containing vinyl alcohol copolymer is performed under substantially anhydrous conditions. The term "substantially anhydrous" means that about 5% by weight or less of water may remain, but desirably, the water content is 1% by weight or less,
In particular, it is less than 0.5% by weight.

At the time of melt molding, a plasticizer such as a polyhydric alcohol can be blended.However, since flexibility can be obtained without using a plasticizer, the use of a plasticizer may deteriorate the properties of a molded product. It is better not to use it.

At the time of melt molding, various additives such as a filler, a colorant and a stabilizer can be blended. Other polymers can be blended within a range that does not impair the purpose of the present invention, or conversely, the above oxyalkylene group-containing vinyl alcohol copolymer can be blended with other polymers.

As the melt molding method, an arbitrary melt molding method such as an injection molding method, an extrusion molding method, and a transfer molding method is employed.

Among the melt molding methods, an injection molding method is particularly important, and it should be said that a water-soluble vinyl alcohol polymer can be injection-molded in an anhydrous or non-plastic state. U.S. Pat.No. 4,618,648, No. 4
No. 675360 discloses that a copolymer of vinyl alcohol and poly (alkyleneoxy) acrylate is injection-molded and extruded, but the alkylene glycol or polyalkylene glycol desorbed and formed during the saponification reaction is disclosed. Works as a plasticizer, so it is actually injection molded with a plasticizer.

As the injection conditions, conditions of a cylinder temperature of 150 to 250 ° C., a mold temperature of 30 to 100 ° C., and an injection pressure of 500 to 2000 kg / cm ² are suitably adopted. Although the oxyalkylene group-containing vinyl alcohol copolymer defined above can be injection-molded, molding is more difficult than other general-purpose molding resins, so strict conditions must be set. .

Extrusion molding is also important in melt molding. Extrusion molding includes blow molding, inflation molding, co-extrusion molding,
Extrusion coating is also included.

In extrusion molding, it is desirable to set the die temperature to 150 to 300 ° C. and the screw compression section temperature to 5 to 30 ° C. higher than the discharge section temperature. Strict conditions must be set during extrusion molding.

Function and Effect of the Invention A copolymer obtained by copolymerizing the monomers constituting the vinyl ester unit (B) and the oxyalkylene allyl ether unit (C) can be obtained by subjecting the copolymer to a saponification reaction. The oxyalkylene group of the oxyalkylene allyl ether unit (C) does not leave.

The oxyalkylene group-containing vinyl alcohol copolymer in the present invention has a vinyl alcohol unit (A) and an oxyalkylene allyl ether unit (C) distributed at an appropriate ratio, and the oxyalkylene unit in the unit (C) Since the weight ratio is set in a specific range, the degree of localization-delocalization of the oxyalkylene unit and the length of the oxyalkylene unit are balanced so as to be suitable for melt molding. In addition, the melt index of the entire copolymer is specified so as to be suitable for melt molding.

Therefore, if a specific molding condition is selected, even if it is a melt molding such as injection molding, it can be a substantially anhydrous (and also does not use a plasticizer), and a smooth melt molding that can be industrially adopted becomes possible.

The obtained molded article has water solubility and flexibility, and also possesses properties such as fragrance retention, oil resistance, antistatic properties, oxygen barrier properties, and heat retention properties based on the vinyl alcohol unit (A). .

In addition, if a crosslinking agent is added during molding or the obtained molded product is subjected to heat treatment or crosslinking agent treatment, the molded product can be made water-resistant.

EXAMPLES Next, the present invention will be further described with reference to examples.

<Production of copolymer> Example 1 Polyoxyethylene monoallyl ether having an average number of moles of added oxyethylene of 25 and vinyl acetate were copolymerized in methanol in the presence of azobisisobutyronitrile,
Then, after the remaining monomer was driven off, a methanol solution of sodium hydroxide was added to perform saponification. The copolymer was filtered off from the slurry produced by the saponification reaction, washed and dried to obtain the desired oxyalkylene group-containing vinyl alcohol copolymer.

Ratio a of vinyl alcohol units (A) in this copolymer
Is 93 mol%, the ratio b of the vinyl acetate unit (B) is 6 mol%, and the ratio c of the oxyethylene allyl ether unit (C) is c.
Was 1 mol%.

 This shows that a + b + c = 100 mol% c = 1 mol% 100a / (a + b) = 94.

Further, it is understood that the weight ratio of the oxyethylene unit to the total weight of (A), (B) and (C) is 19% by weight.

The melt index of this copolymer at a temperature of 210 ° C. and a load of 2160 g was 15 g / 10 min.

The viscosity of a 4% by weight aqueous solution of the copolymer is as follows:
It was 3.6 cps / 20 ° C.

 The characteristic values of the copolymer are shown in Table 1 below.

Examples 2 to 6 Copolymers having various characteristic values as shown in Table 1 were produced according to Example 1.

Comparative Examples 1 to 4 Copolymers having various characteristic values as shown in Table 2 were produced according to Example 1. The copolymers of these comparative examples do not completely have the characteristic values specified in the present application.

<Molding Material> The oxyalkylene group-containing vinyl alcohol copolymers of Examples 1 to 6 and Comparative Examples 1 to 4 were dried to a water content of 0.1% by weight or less, then supplied to an extruder and extruded linearly. Thereafter, the pellets were cut into pellets, and the pellets were subjected to melt molding described below.

<Injection molding> The following injection molding conditions were adopted.

Injection molding machine Nippon Steel Works N100 screw type automatic injection molding machine Screw kneading temperature 200 ° C Discharge section temperature 210 ° C Mold temperature 50 ° C Injection pressure 700kg / cm ² Molding cycle 20 seconds <Extrusion molding> The following extrusion molding conditions are adopted. did.

Extruder Twin screw extruder Screw L 1150mm, D40mmφ L / D = 28.75 Number of revolutions 50rpm Cylinder temperature Compressor 200 ° C T-die temperature 190 ° C <Results> Results of injection molding and extrusion molding and molded products obtained by these moldings Are shown in Tables 3 and 4 below.

Injection / extrusion moldability, water solubility, flexibility, the presence or absence of blocking, and the presence or absence of bleeding were determined as follows.

Injection moldability and extrusion moldability were determined by the presence or absence of rough skin on the surface of the molded product.

For water solubility, test pieces (10
(mm x 50 mm x 1 mm), and the dissolution performance after 10 minutes was observed. In addition, the presence or absence of water turbidity after the test was observed.

：: Dissolution residue is less than 30% by weight △: Dissolution residue is 30% by weight or more and less than 70% by weight ×: Dissolution residue is 70% or more Flexibility is 20 ° C., 60% RH according to JIS K 7203 The condition of the test specimen conditioned for 30 days was observed, and the case where the test piece had flexibility was judged to be ○. Further, the flexural modulus was measured.

For blocking, two test pieces (10 mm x 50 mm x 1 mm) were piled up and observed under a load of 5 g / cm ² at 20 ° C and 72% RH for 16 hours.場合 indicates no attachment, △ indicates slight attachment, and X indicates attachment.

Bleeding is performed by alternately subjecting the molded product to <20 ° C, 65% RH, 16 hours> and <40 ° C, 80% RH, 8 hours>
It was brought 30 times and the state of the surface of the molded product was observed.

From the above results, the copolymers of the examples have practical injection moldability and extrusion moldability, and the molded products have excellent water solubility and flexibility, and cause blocking and bleeding. It turns out there is no.

<Melt moldability of polyvinyl alcohol> For reference, melt mold of polyvinyl alcohol was also attempted.

The following was used as polyvinyl alcohol to be subjected to melt molding.

Is the degree of polymerization, is the degree of saponification (mol%), is 4% by weight.
The viscosity (cps / 20 ° C.) of the aqueous solution having a concentration is a melt index at a temperature of 210 ° C. and a load of 2160 g, and the blending amount (parts by weight) of a plasticizer (glycerin) with respect to 100 parts by weight of polyvinyl alcohol.

PVA-1 200 93 3.2 24 0 PVA-2 300 88 3.3 280 PVA-3 300 80 3.4 34 0 PVA-4 200 93 3.2 29 7 PVA-1, PVA-2, PVA-3, PVA-4 The results obtained when extrusion molding was carried out under the same extrusion molding conditions as in Example 1 were shown below.

Continuation of the front page (51) Int.Cl. ⁶ identification code FI C08F 218/04 C08F 218/04 // B29K 29:00 C08L 29:00 (58) Investigated field (Int.Cl. ⁶ , DB name) C08J 5/00 C08F 216/04 C08F 216/16 C08F 218/04 B29C 45/00 B29C 47/00

Claims (6)

(57) [Claims] 1. The following formula: Wherein each of the vinyl alcohol unit (A), the vinyl ester unit (B) and the oxyalkylene allyl ether unit (C) contains a mol%, b mol%, and c mol%, and R ¹ in (B) is an alkyl group; R ² and R ³ in (C) are H or an alkyl group, R ⁴ in (C) is H, an alkyl group, a phenyl group or a substituted phenyl group, and n is 1
Oxyalkylene that satisfies both the following relationships: 0.1 ≦ c ≦ 20, 50 ≦ 100a / (a + b) ≦ 100, and a melt index of 5 g / 10 min or more at a temperature of 210 ° C. and a load of 2160 g. Group-containing vinyl alcohol copolymer,
A method for melt-molding a water-soluble vinyl alcohol-based polymer, which is melt-molded under substantially anhydrous conditions. Wherein (B) is a vinyl acetate unit, and (C) oxyalkylene units CHR ² -CHR ³ -O _n in
2. The composition of claim 1, wherein the proportion of the total resin is 3 to 40% by weight.
The melt molding method according to the above. 3. The following relationship: 3 ≦ n ≦ 50, 0.1 ≦ c ≦ 5, 80 ≦ 100a / (a + b) ≦ 100, and the oxyalkylene unit CHR ² —CHR ³ — in (C). percentage of the total resin O _n 5
The melt molding method according to claim 1, wherein the amount is from 30 to 30% by weight. 4. The melt molding method according to claim 1, wherein the melt molding is performed substantially without using a plasticizer. 5. The method according to claim 1, wherein the melt molding is injection molding, and the injection molding is performed at a cylinder temperature of 150 to 250 ° C., a mold temperature of 30 to 100 ° C.
Claims 1 to 4 melt-molding method according to characterized in that under the conditions of injection pressure 500~2000kg / cm ^2. 6. The extrusion molding is performed by setting the die temperature to 150 to 300 ° C. and the screw compression section temperature to 5 to 30 ° C. higher than the discharge section temperature. 5. The melt molding method according to claim 1, wherein: