JPH10324775A - Polymer aqueous solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent workability with good compatibility, no separation of aqueous solution of both layers and no increase in viscosity over time, and excellent film transparency, film physical properties and water resistance. Excellent starch-
SOLUTION: A starch (A) and a modified polyvinyl alcohol (B) containing 1 to 20 mol% of α-olefin units having 3 or less carbon atoms are obtained. An aqueous polymer solution having a weight ratio of (B) of 99: 1 to 10:90 and a total concentration of (A) and (B) of 1 to 50% by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polymer aqueous solution composition. More specifically, the present invention relates to a polymer aqueous solution containing starch and a modified polyvinyl alcohol containing 1 to 20 mol% of an α-olefin unit having 3 or less carbon atoms and having good viscosity stability, transparency and film properties.

[0002]

2. Description of the Related Art A mixture of polyvinyl alcohol and starch is water-soluble and has good film-forming ability, and starch is inexpensive. Used in However, since polyvinyl alcohol and starch are both high molecular compounds, they are inferior in compatibility, the stability of the mixed aqueous solution of polyvinyl alcohol and starch is poor, and there is a tendency to separate immediately, and the same mixed aqueous solution was obtained. The film has poor transparency,
The physical properties of the film are not very good. In order to improve the compatibility between polyvinyl alcohol and starch, various modified starches, for example, starch derivatives such as etherified starch, esterified starch, and cationized starch, and starch degradation products such as oxidized starch and dextrin are used. However, these compounds also have insufficient compatibility with polyvinyl alcohol.

On the other hand, it is known that the use of a modified polyvinyl alcohol copolymerized with a long-chain alkyl group having 4 to 20 carbon atoms improves the compatibility with raw starch (Japanese Patent Application Laid-Open No. 56-14544). However, although the stability of the mixed aqueous solution is improved as compared with ordinary polyvinyl alcohol, it is still insufficient, and the physical properties of the film produced from the mixed aqueous solution cannot be said to be satisfactory.
The above-mentioned modified starch has no effect. It is known that the use of a vinyl alcohol-based polymer having a long-chain alkyl having 4 to 50 carbon atoms at the terminal improves the compatibility with starch (Japanese Patent Publication No. 5-75013). Is certainly improved as compared with ordinary polyvinyl alcohol, but the physical properties of the film produced from the mixed aqueous solution cannot be said to be sufficiently satisfactory.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has a good compatibility between starch and polyvinyl alcohol. Another object of the present invention is to provide a polymer aqueous solution which is excellent in workability without separation or increase in viscosity over time, and which is excellent in transparency and physical properties of a film produced from the mixed aqueous solution.

[0005]

The object of the present invention is to provide a starch (A)
And a modified polyvinyl alcohol (B) containing 1 to 20 mol% of α-olefin units having 3 or less carbon atoms,
To provide a polymer aqueous solution in which the weight ratio of (A) and (B) is 99: 1 to 10:90, and the concentration of the total amount of (A) and (B) is 1 to 50% by weight. Achieved by

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Modified polyvinyl alcohol containing 1 to 20 mol% of α-olefin units having 3 or less carbon atoms (hereinafter, polyvinyl alcohol is referred to as P)
VA (may be abbreviated as VA). The content of the α-olefin unit having 3 or less carbon atoms is 1 to 2
It is necessary to be 0 mol%, preferably 1 to 18 mol%, more preferably 2 to 15 mol%. When the content of the α-olefin unit is less than 1 mol%, the known P
It is not so different from VA, the compatibility with starch is not good, the viscosity stability is not good, and the object of the present invention cannot be achieved. α
-When the content of the olefin unit is more than 20 mol%, the hydrophobicity is so strong that the water solubility of the polymer itself becomes poor, resulting in poor compatibility with starch and the object of the present invention is also achieved. Can not.

[0007] The modified PVA used in the present invention preferably has a viscosity-average degree of polymerization (hereinafter abbreviated as degree of polymerization) of 50 to 8000, more preferably 100 to 6000, and even more preferably 100 to 5,000. PVA
The degree of polymerization of the polymer was determined according to JIS-K6726 and the viscosity-average degree of polymerization (P) of the polymer purified after re-saponification was determined from the intrinsic viscosity [η] measured at 30 ° C. in water by the following formula.
It is represented by P = ([η] × 10 ³ /8.29) ^{(1 / 0.62) When the} degree of polymerization is in the above range, the object of the present invention can be more suitably achieved. The degree of saponification of the modified PVA of the present invention is not particularly limited as long as the PVA has a water-soluble or water-dispersible property, but is suitably from 60 to 99.99 mol%, and from 70 to 99.9 mol%. % Is preferable, and 80 to 99.8
Molar% is more preferred. In general, when the degree of saponification is less than 60 mol%, the desired polymer solution is not obtained because the water solubility is reduced. The degree of saponification is 99.99
When it is larger than mol%, there is no problem in performance in particular,
Hard to manufacture. When water resistance is required for a film prepared from a mixed solution of starch and modified PVA, the degree of saponification is preferably 80 mol% or more, more preferably 90 mol% or more, depending on the amount of modification of the α-olefin. .

The modified PV containing 1 to 20 mol% of an α-olefin unit having 3 or less carbon atoms used in the present invention.
A can be obtained by saponifying a copolymer of a vinyl ester and an α-olefin having 3 or less carbon atoms. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. Vinyl acetate is preferred from the viewpoint of obtaining PVA. The α-olefin of the present invention has 3 or less carbon atoms, and includes ethylene and propylene. Ethylene is preferred from the viewpoint of obtaining the polymer composition aimed at by the present invention. Further, the modified PVA of the present invention is modified with an anionic group or a cationic group as required.
By introducing these ionic groups, the water solubility of the modified PVA can be improved, and the viscosity stability of the aqueous polymer solution can be further improved. The type of the monomer unit having an anion group or a cationic group is not particularly limited, and a unit having a carboxyl group is fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride or anhydride. A monomer unit derived from itaconic acid or the like; a monomer unit derived from ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid or the like as a unit having a sulfonic acid group; As units having a cationic group, vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acryl Bromide trimethylammonium chloride, N- acrylamide dimethylamine, allyl trimethyl ammonium chloride, methallyl trimethylammonium chloride, dimethyl allyl amine, include monomeric units of allyl ethyl amine. Among these monomer units, maleic anhydride, a half ester derived from maleic anhydride, itaconic acid, allylsulfonic acid, 2-acrylamide-2-, from the viewpoint of availability and copolymerizability. Methylpropanesulfonic acid, N-acrylamidomethyltrimethylammonium chloride and N-acrylamidoethyltrimethylammonium chloride are more preferred. The content of the monomer having these characteristic groups is usually 10 mol% or less, preferably 8 mol% or less, more preferably 5 mol% or less.

The modified PVA of the present invention may contain a unit other than a vinyl alcohol unit and a vinyl ester unit as long as the effects of the present invention are not impaired. Examples of such units include acrylic acid and salts thereof; acrylic esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate and i-propyl acrylate; methacrylic acid and salts thereof; methyl methacrylate;
Methacrylic esters such as ethyl methacrylate, n-propyl methacrylate and i-propyl methacrylate; acrylamide; acrylamide derivatives such as N-methylacrylamide and N-ethylacrylamide; methacrylamide; N-methylmethacrylamide; N-ethyl Methacrylamide derivatives such as methacrylamide; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, and i-propyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride, vinylidene chloride, vinyl fluoride, and fluoride. Vinyl halides such as vinylidene; allyl compounds such as allyl acetate and allyl chloride; maleic acid, its salts or esters; itaconic acid, its salts or esters; vinyl Vinyl silyl compounds such as trimethoxysilane, isopropenyl acetate and the like. The content of these units is preferably 10 mol% or less,
More preferably, it is not more than 3 mol%, more preferably not more than 3 mol%.

[0010] As starch, raw starch, raw starch decomposition product,
Starch derivatives and amylose are used. Raw starch includes wheat, corn, rice, potato, sweet potato, tapioca,
Examples include starch obtained from sago palm or the like, and wheat starch, corn starch, and potato starch are generally suitable. Examples of raw starch degradation products include oxidized starch and dextrin, and oxidized starch is suitable. Examples of the starch derivative include etherified starch, esterified starch, and cationized starch. The mixing ratio of the starch (A) and the modified PVA (B) having an α-olefin unit having 3 or less carbon atoms is suitably (A) :( B) = 99: 1 to 10:90 by weight mixing ratio, (A) :( B) = 97: 3-10: 90: is preferred, and (A) :( B) = 95: 5-10: 90 is more preferred. When the main purpose is to improve the standing viscosity stability of the aqueous starch solution, it is important that (B) is at least 1 part by weight based on 100 parts by weight of the total amount of starches (A) and (B). It is preferably at least 3 parts by weight, more preferably at least 5 parts by weight. When (B) is less than 1 part by weight, (B)
Has no effect. On the other hand, when the main purpose is to improve the quality of the starch film, it is important that the amount of (B) is at least 10 parts by weight, preferably at least 15 parts by weight, based on 100 parts by weight of the total amount of starches (A) and (B). It is suitable that the amount is not less than 20 parts by weight, more preferably not less than 20 parts by weight. Conversely, if (B) is less than 10 parts by weight, there is no difference in physical properties from (B) itself.

In the polymer aqueous solution of the present invention, it is important that the total concentration of the starch (A) and the modified PVA (B) having an α-olefin unit having 3 or less carbon atoms be 1 to 50% by weight. Yes, by setting the concentration within this range,
A polymer aqueous solution having excellent viscosity stability, excellent transparency, and excellent coatability can be obtained. Suitable concentrations are 1.5% by weight or more for the lower limit, more preferably 2% by weight or more, and the upper limit is preferably 45% by weight or less, more preferably 40% by weight or less.
% By weight or less. The aqueous polymer solution of the present invention thus obtained has the following features. The aqueous polymer solution of the present invention comprises starch and other known PVA-based polymers (normal PVA).
A, anion-modified PVA, cation-modified PVA, nonionic-modified PVA such as long-chain alkyl group, and other modified PV
Compared to the aqueous solution of the mixture with A), the aqueous solution has better storage stability, is less likely to undergo layer separation, and has less change with time in viscosity and is easier to handle. This is presumably because the starch and the modified PVA having an α-olefin unit having 3 or less carbon atoms have good compatibility, and the starch is uniformly dispersed in the aqueous solution without much aggregation. A PVA copolymer obtained by copolymerizing a long-chain alkyl group also has an effect of slightly improving the stability of an aqueous solution with raw starch as compared with ordinary PVA, but the polymer aqueous solution of the present invention is more stable. It has a stabilizing effect similar to that of a vinyl alcohol-based polymer having a long-chain alkyl having 12 carbon atoms at the terminal. In addition, a PVA-based copolymer obtained by copolymerizing a long-chain alkyl group has no effect in an aqueous solution with oxidized starch, but the aqueous polymer solution of the present invention is stable. Further, among the modified PVAs having an α-olefin unit having 3 or less carbon atoms of the present invention, the aqueous solution of the composition of the α-olefin modified PVA having an anion group as a third component with starch is extremely stable.

The film formed from the aqueous polymer solution of the present invention is homogeneous, has good transparency, and has higher strength, elongation and elasticity than a mixture of other PVA polymer and starch. It has high modulus and toughness and has excellent coating mechanical properties. 4 to 5 carbon atoms at the end, which have excellent compatibility with starch
The reason why the vinyl alcohol polymer having 0 long-chain alkyl does not have satisfactory film properties is that it is necessary to increase the long-chain alkyl introduction efficiency from the viewpoint of increasing the compatibility with starch.
This is probably because the degree of polymerization of PVA is low. The reason that the film formed from the polymer aqueous solution of the present invention has the above-mentioned properties is that the α-olefin unit having 3 or less carbon atoms acts to enhance the interaction with the starch, and the hydrophilic PVA portion is used. It is considered that they have a function of preventing aggregation of starches and dispersing them uniformly in fine particles. This effect is moderately hydrophobic α-
It appears that the presence of the olefin is working effectively. Further, among the modified PVAs having α-olefin units having 3 or less carbon atoms of the present invention, a film formed from an aqueous polymer solution comprising α-olefin-modified PVA having an anionic group as a third component and starch is extremely excellent. It has the mechanical properties of a coated film. Moreover, the film formed from the aqueous solution of the polymer of the present invention has extremely excellent water resistance as compared with a mixture of another PVA-based polymer and starch. It is considered that the reason for this is that the water resistance of the modified PVA itself is reflected by the same action mechanism as described above.

The aqueous polymer solution of the present invention comprises a modified PVA having starch (A) and α-olefin units having 3 or less carbon atoms.
(B) A method in which both are mixed with powder and then water is added or poured into water to gelatinize, and (A) and (B) are separately gelatinized by adding water separately. It can be obtained by any method such as a method. Plasticizers, colorants, fillers, salts, boric acid or borax, other water-soluble polymers, surfactants, defoamers and other additives may be added to the mixture of the two.

The aqueous polymer solution of the present invention is also excellent in coating properties, and therefore is particularly useful as a paper processing agent, a sizing agent for fibers, particularly a sizing agent for warp and an adhesive, Since it has excellent physical properties, it can be used as a molded material such as a film.

[0015]

The present invention will be described in more detail with reference to examples. In the following, “parts” and “%” mean “parts by weight” and “% by weight”, respectively, unless otherwise specified.
In the following description, the viscosity is a value measured at 30 ° C. and a rotor rotation speed of 12 rpm using a B-type viscometer manufactured by Tokyo Keiki.

As a reference example, PVA having an ethylene unit
An example of a method for synthesizing a polymer will be described. Reference Example 50 kg of vinyl acetate and 9.2 kg of methanol were charged into a 100-L pressure reaction tank equipped with a stirrer, a nitrogen inlet, an ethylene inlet, and an initiator inlet, and heated to 60 ° C., followed by nitrogen bubbling for 30 minutes. The system was replaced with nitrogen. Then, ethylene was introduced and charged so that the pressure in the reaction tank became 6 kg / cm ² . A 1.4 g / L solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) dissolved in methanol was prepared as an initiator, and the solution was replaced with nitrogen by bubbling with nitrogen gas.
After adjusting the internal temperature of the reaction vessel to 60 ° C., 56 mL of the above-described initiator solution was injected to initiate polymerization. During the polymerization, ethylene was introduced to maintain the reactor pressure at 6 kg / cm ² and the polymerization temperature at 60 ° C.
Continuously added at hr. After 6 hours, when the conversion reached 30%, the mixture was cooled to stop the polymerization. After the reactor was released and ethylene was removed, nitrogen gas was bubbled through to completely remove ethylene. Then, unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution. To the solution adjusted to 20%, a NaOH methanol solution (10% concentration) having a molar ratio of 0.06 (moles of NaOH / moles of polyvinyl acetate) was added, and saponification was performed for 1 hour while maintaining the temperature at 40 ° C. The degree of saponification of the resulting modified PVA was 98.9 mol%.

A methanol solution of PVAc obtained by removing the polymerized and unreacted vinyl acetate monomer is precipitated in n-hexane, and reprecipitated by dissolving in acetone three times.
It dried under reduced pressure at ° C, and obtained purified PVAc. The amount of ethylene modification determined by measuring the alkali consumption of the PVAc was 5 mol%. After saponification of the above methanol solution of PVAc at an alkali molar ratio of 0.2, methanol soxhlet was performed for 3 days and then dried to obtain purified PVA. The average degree of polymerization of the PVA was 1,750 when measured according to JIS K6726 of a conventional method.

In the above method, PVA-based polymers having various α-olefin units were obtained as shown in Table 1 by changing the amount of ethylene introduced or changing ethylene to propylene.

[0019]

[Table 1]

Example 1 A mixture of modified PVA (P-1) having 5 mol% of ethylene and corn starch was heated and dissolved in an autoclave at 125 ° C. for 2 hours to prepare an aqueous solution having a solid content of 7%.
The viscosity of the aqueous solution at 20 ° C. was measured immediately after the preparation of the aqueous solution and one week later. The state of the aqueous solution one week later was also observed. Table 2 shows the results.

Example 2 and Comparative Examples 1 to 3 As Example 2, an ethylene-modified PVA (P-2) having a different amount of ethylene modification and a different degree of polymerization was prepared in the same manner as in Example 1.
Was examined. As Comparative Example 1, polymerization degree 1750, saponification degree
98.5 mol% of PVA (Kurarepovar PVA-117) /
The corn starch system was used as Comparative Example 2 for PVA having a polymerization degree of 550 and a saponification degree of 98.5 mol% (Kurarepovar PVA-10).
5) The corn starch system was measured in the same manner as in Example 1 for a solution of corn starch alone as Comparative Example 3. Table 2 shows the results.

A solution using PVA-117 and PVA-105 has a large change in viscosity with time, and is easily separated. Corn starch alone also tends to gel immediately. On the other hand, it can be seen that the solution using ethylene-modified PVA has a small change in viscosity over time and also has a good storage stability.

[0023]

[Table 2]

Example 3 Modified PVA (P-3) copolymerized with 8 mol% of ethylene and 2 mol% of maleic anhydride, and oxidized starch MS-3800
(Manufactured by Nippon Shokuhin Kako Co., Ltd.) at a ratio of 50:50 (weight basis) was heated and dissolved in hot water at 95 ° C. for 3 hours to prepare an aqueous solution having a solid content of 5%. 20 of this aqueous solution
The viscosity at 0 ° C. was measured immediately after the preparation of the aqueous solution and after 3 days. The time during which the aqueous solution having a concentration of 7% causes layer separation at 50 ° C. was measured. Table 3 shows the results.

Examples 4 to 6 and Comparative Examples 4 to 8 As Examples 4 to 6, the α-olefin-modified PVAs (P-4 to P-6) shown in Table 1 were examined in exactly the same manner as in Example 3. As Comparative Example 4, a terminal alkyl group-modified PV having C ₁₂ H ₂₅ at the terminal and having a polymerization degree of 1700 and a saponification degree of 98.5 mol%
A (PVA-A), polymerization degree 550 having a C ₁₂ H ₂₅ at the end as a comparative example 5, a saponification degree of 88.0 mol% of terminal alkyl group-modified PVA (PVA-B), 2 moles of maleic anhydride Comparative Example 6 % Of modified PVA (PVA-C) having a polymerization degree of 1800 and a saponification degree of 98.5 mol%, and a polymerization degree of lamination of 0.6 mol% of lauryl vinyl ether of Comparative Example 700
, PVA modified with a long-chain alkyl group having a saponification degree of 98.6 mol%
(PVA-D), as Comparative Example 8, 3 versatic acids
Mole%, 1 mole% of itaconic acid copolymerized, 700
Copolymerized modified PVA with a saponification degree of 96.5 mol% (PVA-E)
A mixed aqueous solution (solid content concentration: 5%) with oxidized starch MS-3800 was prepared in the same manner as in Example 3, and the viscosity was measured. Table 3 shows the results.

A solution using a terminal alkyl group-modified PVA and a modified PVA obtained by copolymerizing a carboxylic acid and a long-chain alkyl group has a large change with time in viscosity, tends to gel, and is easily separated, and has a problem in handling. On the other hand, it can be seen that the solution using PVA modified with an α-olefin having 3 or less carbon atoms has a small change with time in viscosity and also has a good storage stability.

[0027]

[Table 3]

Example 7 A mixture of modified PVA (P-1) having 5 mol% of ethylene and oxidized starch MS-3800 at various ratios was mixed with 95%
The solution was heated and dissolved in hot water of 3 ° C. for 3 hours to prepare an aqueous solution having a solid content of 5%. This aqueous solution was poured onto a glass plate on which polyethylene terephthalate was adhered, and water was evaporated at 20 ° C. to form a film. The film is 20 ° C x 84%
The strong elongation of the film conditioned for one week at RH was measured. Table 4 shows the results. Measuring method of physical properties of film Shimadzu Autograph DSC-100 type (manufactured by Shimadzu Corporation) used Sample width 10 mm, thickness 45 ± 5 μm, measurement length 50 mm Peeling speed 500 mm / min

Examples 8 to 9 and Comparative Examples 9 to 11 Examples 8 to 9 were the same as in Example 7 except that the amount of ethylene modification and the degree of polymerization were different, and that ethylene modified PVA having a carboxyl group (P-2) was used. To 3). As Comparative Example 9, PVA having a polymerization degree of 1750 and a saponification degree of 98.5 mol% (Kuraray Poval PVA-117), Comparative Example 1
The degree of polymerization of maleic anhydride copolymerized by 2 mol% as 0 was 18
00, modified PVA (PVA-C) having a saponification degree of 98.5 mol%,
Comparative Example 11 having a degree of polymerization of 100 having C ₁₂ H ₂₅ at the terminal,
PVA modified with a terminal alkyl group having a saponification degree of 97.5 mol% (PV
The measurement was performed after forming a film in the same manner as in Example 7 using AF). Table 4 shows the results.

The coating using PVA-117 and 2 mol% maleic anhydride-modified PVA (PVA-C) had poor compatibility between PVA and oxidized starch, and the obtained coating was non-uniform. The coating had a high elastic modulus and a low elongation when the mixing ratio of the oxidized starch was increased, and as a result, the coating was extremely low in toughness. Terminal alkyl group-modified PVA
The coating using (PVA-F) had good compatibility between PVA and oxidized starch, but had very small strength, elongation and toughness in all compositions. On the other hand, it is understood that the film using the ethylene-modified PVA-based polymer has a good compatibility between the PVA and the oxidized starch, and has excellent film properties with large strength, elongation, elastic modulus and toughness. .

[0031]

[Table 4]

1) Judgment of transparency of the film: judged in 5 stages by visual observation 5: transparent, 4: almost transparent, 3: translucent, 2: ground glass, 1: no transparency

Example 10 From a mixture of modified PVA (P-1) having 5 mol% of ethylene and oxidized starch MS-3800 at various ratios,
An aqueous solution (solid content: 5%) was prepared in the same manner as in Example 7 to form a film. The film was immersed in water at 20 ° C. for 24 hours and then taken out, and the degree of swelling and the dissolution rate of the film were measured. Table 5 shows the results. Measurement method of swelling degree and dissolution rate of film Sample 50mm × 30mm, thickness 45 ± 5μm Water 100ml, 20 ° C × 24 hours Swelling degree (times) = weight of film after water immersion / 105 ° C after water immersion ×
Film weight after drying for 5 hours Elution rate (%) = (Pure weight of film before water immersion-105 after water immersion
℃ x 5 hours after drying) x 100 / pure weight of coating before immersion in water

Example 11 and Comparative Example 12 As Example 11, ethylene-modified PVA (P-
2) was examined. As Comparative Example 12, PVA having a polymerization degree of 1750 and a saponification degree of 98.7 mol% (Kuraray Povar PVA-11)
7) was similarly examined. Table 5 shows the results.

The coating using PVA-117 has a large degree of swelling and elution. On the other hand, a film using ethylene-modified PVA has a small degree of swelling and a small elution rate, indicating that the film is excellent in water resistance.

[0036]

[Table 5]

[0037]

The aqueous polymer solution of the present invention has good compatibility with starch and polyvinyl alcohol, and is excellent in workability without causing a phase separation of the mixed aqueous solution of the two and the increase in viscosity over time. It is excellent in transparency, film properties and water resistance of the film produced from the mixed aqueous solution, and also excellent in coatability, especially for paper processing agents, fiber sizing agents, especially warp sizing agents, adhesives, etc. It can be suitably used in the field.

Claims (2)

[Claims] Claims 1. A starch (A) and a modified polyvinyl alcohol (B) containing 1 to 20 mol% of an α-olefin unit having 3 or less carbon atoms, wherein the weight ratio of (A) to (B) is 99: An aqueous polymer solution having a concentration of 1 to 10:90 and a total concentration of (A) and (B) of 1 to 50% by weight. 2. The aqueous polymer solution according to claim 1, wherein the α-olefin having 3 or less carbon atoms is ethylene.