JPH0575014B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention consists of starch (A), a polyvinyl alcohol polymer (B) having a long chain alkyl group with 4 to 50 carbon atoms at the end, and polyvinyl alcohol (C), which are highly compatible. The present invention relates to a starch-based polymer composition with good properties. Conventional technology Polyvinyl alcohol (hereinafter abbreviated as PVA)
A mixture of starch and starch has been used as a warp glue for fibers, a paper processing agent, etc. because it is water-soluble and has good film-forming ability, and starch is inexpensive. However, since PVA and starch are both polymeric compounds, they have poor compatibility, and a mixed aqueous solution of PVA and starch has poor stability and tends to separate quickly.
Furthermore, the film obtained from this same mixed aqueous solution has poor transparency and film physical properties that are not very good. In order to improve the compatibility between PVA and starch, various modified starches such as starch derivatives such as etherified starch, esterified starch, and cationized starch, and starch decomposition products such as oxidized starch and dextrin can be used as starch. Although widely attempted, starch derivatives have the disadvantage of high cost, while starch degradation products have a lower molecular weight than the original starch and therefore
Although the stability of the mixed aqueous solution with PVA is improved,
The physical properties of the film made from this mixed aqueous solution are not very good, and may even lead to poor results. That is, even if these modified starches are used, their compatibility with PVA is still insufficient. On the other hand, it is known that the use of modified PVA copolymerized with a long-chain alkyl group having 4 to 20 carbon atoms improves the compatibility with raw starch (Japanese Unexamined Patent Application Publication No. 1989-1999-1).
14544, JP-A-56-55440), although the stability of the mixed aqueous solution is certainly improved compared to ordinary PVA, it still tends to gel, and the physical properties of the film produced from the mixed aqueous solution are also sufficiently satisfactory. I cannot say that I will. Moreover, the above-mentioned modified starches have no effect. The production technology of PVA polymers having a long hydrocarbon chain alkyl group at the end is already known (Japanese Patent Publication No. 48-1831,
58−108207). However, the technology regarding the compatibility between this PVA-based polymer and starch is not yet known. Problems to be solved by the invention Raw starch is water-soluble, cheap, and easily available, while PVA is a water-soluble synthetic polymer compound with stable quality and many brands. Although it is used in many fields due to its excellent film-forming ability, it has the disadvantage that it is more expensive than starch because it is a synthetic polymer. For this reason, a mixture of PVA and starch is used, which has physical properties intermediate between the two. However, since these two substances are essentially not compatible, the stability of the mixed aqueous solution is poor, and there are various problems in handling such as separation and increase in viscosity over time. The physical properties of molded articles produced from the mixed aqueous solution are also not satisfactory. Means for Solving the Problem Under these circumstances, the inventor of the present invention made extensive studies and found that a mixture of starch (A) and PVA (C) has a long chain with 4 to 50 carbon atoms at the end. has an alkyl group
When PVA-based polymer (B) is added, the mixture has very good compatibility, the stability of this mixed aqueous solution is improved, and the change in viscosity of the mixed aqueous solution over time is small. The present invention was completed by discovering that the film has excellent transparency and good physical properties. The terminal hydrophobic group-modified PVA polymer (B) having a long chain alkyl group having 4 to 50 carbon atoms at the terminal used in the present invention will be explained. The terminal long-chain alkyl group is suitably one having 4 to 50 carbon atoms. When the number of carbon atoms is less than 4, it is not much different from unmodified PVA and its compatibility with starch is also poor. In addition, polymers with carbon numbers exceeding 50 have too strong hydrophobicity, resulting in poor water solubility of the polymer itself, resulting in poor compatibility with starch, and the purpose of the present invention cannot be achieved. is suitable, but preferably has 8 to 24 carbon atoms. Examples of such groups include long-chain alkyl groups with 4 to 50 carbon atoms, branched alkyl groups, alkylaryl groups, etc., which have a linking group composed of atoms such as O, N, and S. Also includes things. Next, the degree of polymerization of the polymer is closely related to the amount of terminal groups introduced, but is preferably 10 to 3000, preferably 50 to 3000.
2500 is appropriate. There are no particular restrictions on the degree of saponification, but a degree of saponification of 50 mol% or more is usually used.
Preferably it is 70 mol% or more. The polymer may also contain small amounts of units in addition to vinyl alcohol units and residual vinyl ester units such as vinyl acetate, examples of which include α- units such as ethylene, propylene, and isobutene.
Olefin, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, maleic anhydride or their salts or alkyl esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, alkyl vinyl ether, N,N- Examples include dimethylacrylamide, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, vinyl propionate, vinyl versatate, 2-acrylamidopropanesulfonic acid and its salts. However, it is not necessarily limited to these. The PVA-based polymer (B) having a long chain alkyl group with 4 to 50 carbon atoms at the end as described above can be produced by several methods, but industrially it is
The most preferred method is to polymerize a monomer mainly consisting of a vinyl ester such as vinyl acetate in the presence of a mercaptan having 50 long-chain alkyl groups, and then saponify the resulting polyvinyl ester polymer by a conventional method. In addition, PVA (C) includes ordinary PVA with a degree of polymerization of 100 to 3000, preferably 200 to 2500, and a degree of saponification of 50 mol% or more, preferably 70 mol% or more, as well as PVA having a long chain alkyl group at the end. Similar to the system polymer, it may be anionically modified, cationically modified, or nonionically modified. On the other hand, as the starch (A), starches obtained from wheat, corn, rice, horse reishiyo, amashiyo, tapioca, sago palm, etc. are used, but wheat starch and corn starch are generally suitable. Decomposition products of starch such as dextrin and oxidized starch produced from the raw starches mentioned above, or starch derivatives such as etherified starch, esterified starch, and cationized starch may also be used. Starch (A) and PVA with a long chain alkyl group at the end
The blending ratio of system polymer (B) and PVA (C) is starch (A)
A wide range of effects can be seen, from those containing the majority of starch to those containing a small amount of starch. i.e. (A)100
[(B)+(C)] is suitably 2 to 10,000 parts by weight, preferably 5 to 5,000 parts by weight. If [(B) + (C)] is less than 2 parts per 100 parts by weight of (A), the physical properties are not different from those of starch, and [(B) + (C)] is less than 2 parts by weight.
If it exceeds 10,000 parts by weight, the starch has no effect. Here, (C) is 1 to 10,000 per 100 parts by weight of (B).
Parts by weight are appropriate, preferably 1 to 5000 parts by weight. In addition, the ratio of the PVA polymer (B) having a long chain alkyl group at the end to the starch (A) is 1 to 3000 parts by weight, preferably 5 to 100 parts by weight of (A). ~
1000 parts by weight is preferred. When the main purpose is to improve the storage stability of the starch aqueous solution, it is appropriate to add (B) to 100 parts by weight of starch (A) at least 1 part by weight, more preferably at least 5 parts by weight. If (B) is less than 1 part by weight per 100 parts by weight of starch (A), the effect of adding (B) is not so great. On the other hand, if the main purpose is to improve the quality of the starch film, use starch (A).
It is appropriate for (B) to be at least 10 parts by weight, preferably at least 20 parts by weight, per 100 parts by weight. On the other hand, if the PVA polymer (B) having a long chain alkyl group at the end exceeds 5,000 parts by weight per 100 parts by weight of starch (A), the effect of adding starch is lost. The starch-based polymer composition according to the present invention, which is composed of a mixture of such starch (A), a PVA-based polymer (B) having a long-chain alkyl group at the terminal, and PVA (C), has the following characteristics. . That is, the aqueous solution of the composition of the present invention contains starch (A) and
Compared to an aqueous solution of PVA(C), the aqueous solution is highly transparent, has good storage stability, and has very little change in viscosity over time, making it easy to handle. This is starch (A) and PVA polymer (B) with long chain alkyl groups at the end.
The starch is dispersed uniformly in an aqueous solution without much agglomeration due to its very good compatibility with the PVA polymer (B), which has a long chain alkyl group at the end.
Since it has good compatibility with PVA(C), it seems that the overall compatibility is good and the solution stability is also good. PVA-based polymers in which long-chain alkyl groups are randomly copolymerized also have the effect of somewhat improving the stability of aqueous solutions with starch compared to ordinary PVA, but the aqueous solutions of the compositions of the present invention are even more stable. It is. PVA polymer with long chain alkyl group at the end
(B) has a unique interaction with starch (A).
It can be estimated from the viscosity behavior of a mixed aqueous solution of and (A).
That is, a mixture of a PVA polymer having a C ₁₂ H ₂₅ - alkyl group at the end, a degree of polymerization of 100, and a degree of saponification of 99.2 mol% and cornstarch in various proportions was poured into water and thoroughly stirred. The mixture was gelatinized by heating at 95° C. for 2 hours to prepare an aqueous solution having a concentration of 5% by weight. The viscosity of this aqueous solution at 90°C was measured using a B-type viscometer. Next, PVA with a polymerization degree of 550 and a saponification degree of 98.5 mol%
(Kuraray Poval PVA-105)/Corn starch system was similarly measured for viscosity. The results are shown in Figure 1. In Figure 1, the solid line 1 represents the PVA polymer/cornstarch system with a long chain alkyl group at the end, and the dotted line 2 represents the viscosity behavior of the PVA-105/cornstarch system. be. The viscosity of the PVA-105/cornstarch aqueous solution decreases as the PVA content increases, but it has a long chain alkyl group at the end.
PVA-based polymer/cornstarch-based aqueous solutions generally have higher viscosity than PVA-105/cornstarch-based aqueous solutions (the viscosity of the aqueous solution of this PVA-based polymer itself is lower than that of PVA-105), Moreover, PVA has a long chain alkyl group at the end.
It shows a maximum when the content of the system polymer is 10 to 30% by weight, and it clearly has a long chain alkyl group at the end.
This shows that PVA-based polymers and corn starch have a unique interaction. Modified PVA copolymerized with long-chain alkyl groups also has the effect of improving the stability of mixed aqueous solutions, but
Even so, it still has a tendency to gel, and modified starches are said to be ineffective. On the other hand, PVA polymers with long chain alkyl groups at the end
(B) has a long chain alkyl group as a terminal hydrophobic group and a PVA moiety as a hydrophilic group, which are bonded together in a block manner, so it has extremely surface active ability.
It is thought that the long-chain alkyl group present at the end improves compatibility with starch, and the PVA part at one end has affinity with other PVA, resulting in very good compatibility of this mixture. This point is a copolymerized modified PVA containing randomly long-chain alkyl groups.
This is different. The change in aqueous viscosity of the composition of the present invention over time is very small, which indicates that it is effective in preventing the aging phenomenon of starch. Starch generally consists of amylose and amylopectin, and this aging phenomenon is said to be caused by crystallization of amylose in starch. It is a known fact that this amylose interacts with higher fatty acids and has good compatibility. The PVA-based polymer used in the present invention, which has a long-chain alkyl group at the end, also has a long-chain alkyl group at the end, similar to higher aliphatic groups, so it interacts with amylose, and also has a long-chain alkyl group at the end. The PVA part facilitates dispersion in water.
This is thought to be the reason why starch has the effect of preventing starch from aging. On the other hand, little is known about its interaction with amylopectin, another component in starch, but the PVA-based polymer with a long-chain alkyl group at the end used in the present invention is similar to amylopectin and amylose. It was observed that there was an interaction between That is, it has amylopectin separated from cornstarch and a C ₁₂ H ₂₅ - long chain alkyl group at the end, a polymerization degree of 280, and a saponification degree of 98.5 mol%.
A mixture of PVA-based polymer and PVA polymer in various proportions was poured into water, heated at 95℃ for 2 hours to gelatinize it, and the concentration was determined.
A 1.5% by weight aqueous solution was prepared. 20 of this aqueous solution
The viscosity and permeability at °C were measured.

[Table] ◎ Transmittance measurement method for aqueous solution Used Hitachi spectrophotometer (manufactured by Hitachi, Ltd.) Wavelength 650 nm Cell width 10 mm The results are shown in Table 1. The viscosity at 20℃ of 1.5% by weight of only PVA-based polymers having long-chain alkyl groups at the ends is about 1 centipoise, which is almost the same as water. As the ratio of coalescence increases, the viscosity increases and the transmittance also increases. Polymerization degree 550, saponification degree 98.5 mol%
An aqueous solution of ordinary PVA (Kuraray Poval PVA-105) and amylopectin has a viscosity of approximately 8 centipoise, which does not change even when PVA-105 is added, and the transmittance is 16 cm.
It remained almost unchanged at ~18%. From this, it is presumed that PVA-based polymers having long-chain alkyl groups at their terminals also have a unique interaction with amylopectin. This is a feature not found in PVA copolymerized with long-chain alkyl groups and other PVA-based polymers. In this way, it has a long chain alkyl group at the end.
The interaction of the PVA-based polymer not only with amylose but also with amylopectin is thought to be the reason for its good compatibility not only with raw starch but also with oxidized starch and other modified starches. Furthermore, the film formed from the aqueous solution of the composition of the present invention is extremely homogeneous and has good transparency.
Compared to a mixture consisting only of the polymer (C) and starch (A), the film has higher strength and elongation, and exhibits excellent film properties. The reason for this is that the long chain alkyl group at the end of the PVA polymer (B), which has a long chain alkyl group at the end, works to enhance the interaction with starch (A).
This is thought to be because the hydrophilic PVA part on the other hand prevents the starches from agglomerating together, and also has good compatibility with PVA (C), so that the starch (A) is uniformly dispersed in the form of fine particles. This effect is thought to be very effective due to the block-like presence of the hydrophobic long-chain alkyl group and the hydrophilic PVA moiety. Starch (A) and PVA with a long chain alkyl group at the end
The system polymer (B) and PVA (C) can be mixed by mixing the three in powder form and then adding water or pouring it into water to gelatinize it, or (A), (B), and (C). Any method may be used, such as gelatinizing each separately and then mixing them. Further, when gelatinizing raw starch, it may be done under normal pressure or high pressure, but it is preferable to use starch gelatinized under high pressure in terms of physical properties. The mixture of both contains plasticizers, colorants, fillers,
Salts, boric acid, borax, other water-soluble polymers, surfactants, and other additives may be added. The composition of the present invention is a sizing agent for textiles, particularly a sizing agent for warp yarns,
It can be used as a paper processing agent, adhesive, film forming agent, etc. Next, as a reference example, an example of a method for producing a PVA-based polymer having a long-chain alkyl group at the terminal will be described. Reference example: 960 parts of vinyl acetate (hereinafter abbreviated as VAc), 230 parts of methanol, and 0.99 parts of n-dodecylmercaptan (hereinafter abbreviated as n-DDM) were placed in a reaction vessel, and the inside was sufficiently replaced with nitrogen, and the outside temperature was raised to 65°C. Give it to me,
When the internal temperature reached 60°C, 10 parts of methanol containing 0.174 parts of 2,2-azobisisobutyronitrile was added. VAc/ immediately containing 15.3 parts of n-DDM
60 parts of methanol solution (VAc concentration 80%) was added uniformly over 5 hours. The polymerization rate after 5 hours is
It was 48.2%. After 5 hours, the container was cooled and the remaining VAc was expelled from the system together with methanol under reduced pressure while adding methanol to obtain a methanol solution of PVAc (concentration 72%). Take a portion of this methanol solution, add a methanol solution of NaOH so that the PVAc concentration is 50%, [NaOH]/[VAc] = 0.1 (molar ratio), and hold at 40°C.
PVA with a saponification degree of 99.2% was obtained.
The degree of polymerization calculated from [η] in acetone using the Nakajima equation was 82. Actions and Effects of the Invention In the PVA polymer having a long chain alkyl group at the end, the long chain alkyl group at the end increases the interaction with starch, and one PVA part has the function of stabilizing the dispersion of starch in water. It also has good compatibility with other PVA, so it has good storage stability in aqueous solutions and is effective in preventing starch from aging. In addition, since the starch is uniformly present in the form of fine particles, the films formed from these aqueous solutions are homogeneous, have good transparency, and have excellent film properties. EXAMPLES The present invention will be specifically explained below with reference to Examples, but the following Examples are not intended to limit the present invention in any way. All percentages and parts in the examples are based on weight unless otherwise specified. The details of the PVA polymer having a long-chain alkyl group at the end used are shown in Table 2.

【table】

[Table] Example 1 Generally, ordinary PVA and oxidized starch are least compatible at a ratio of 50:50 (based on weight). Therefore, as Example 1 of the present invention, oxidized starch Mermaid M-200 (manufactured by Shikishima Starch Co., Ltd.) and polymerization degree
1750, a mixture of PVA with a saponification degree of 98.5 mol% (Kuraray Poval PVA-117) at a ratio of 50:50 (by weight), with a long chain alkyl group at the end.
Add 5 to 70 parts of PVA-based polymer (P-2) to 100 parts of oxidized starch and add it to water.
An aqueous solution with a solid content concentration of 10% was prepared by heating and dissolving for a period of time. The viscosity of the aqueous solution at 20°C was measured immediately after preparation of the aqueous solution and 2 days later. The state of the aqueous solution after 2 days was also observed. As a comparative example, a sample to which P-2 was not added was also measured in the same manner. The results are shown in Table 3. The solution without P-2 showed a large change in viscosity over time and was easily separated.
On the other hand, it has a long chain alkyl group at the end.
It can be seen that the solution containing the PVA polymer (P-2) has a small change in viscosity over time and good storage stability.

【table】

[Table] Example 2 As Examples 2 to 6 of the present invention, 5% concentration of PVA-based polymers having long chain alkyl groups at various terminals was added to 45 parts of an aqueous cornstarch solution (concentration 5%) gelatinized at 120°C. 10 parts of an aqueous solution with a polymerization degree of 550 and a saponification degree of
98.5 mol% PVA (Kuraray Poval PVA-105)
A mixed aqueous solution was prepared by adding 45 parts of a 5% aqueous solution of. The viscosity of this aqueous solution at 20°C was measured immediately after dissolution and 2 days later. As Comparative Example 2, 45 parts of a cornstarch aqueous solution (concentration 5%) gelatinized at 120°C was added with a polymerization degree of 1750,
PVA with saponification degree of 98.5 mol% (Kuraray Poval PVA
A mixed aqueous solution was similarly prepared by adding 10 parts of a 5% aqueous solution of PVA-117) and 45 parts of a 5% aqueous solution of PVA-105, and the viscosity was measured. As comparative example 3, 120
An aqueous solution of corn starch gelatinized at ℃ (concentration 5
%) 45 parts copolymerized with 0.6 mol% lauryl vinyl ether, polymerization degree 700, saponification degree 98.6 mol%.
Long-chain alkyl group copolymerized modified PVA (PVA-L)
A mixed aqueous solution was similarly prepared by adding 10 parts of a 5% aqueous solution of PVA-105 and 45 parts of a 5% aqueous solution of PVA-105, and the viscosity was measured. As Comparative Example 4, 45 parts of an aqueous solution of cornstarch (concentration 5%) gelatinized at 120°C was copolymerized with 3 mol% of versatile acid and 1 mol% of itaconic acid to give a degree of polymerization of 700 and a degree of saponification of 96.5 mol%. A mixed aqueous solution was similarly prepared by adding 10 parts of a 5% aqueous solution of PVA (PVA-V) and 45 parts of a 5% aqueous solution of PVA-105, and the viscosity was measured.
As Comparative Example 5, 5% of a PVA polymer (P-8) having a long chain alkyl group at the end was added to 45 parts of an aqueous solution of cornstarch (concentration 5%) gelatinized at 120°C.
A mixed aqueous solution was prepared in the same manner by adding 10 parts of a 5% aqueous solution of PVA-105 and 45 parts of a 5% aqueous solution of PVA-105, and its viscosity was measured. The results are shown in Table 4. The long chain alkyl group at the end needs to have 4 or more carbon atoms; if it is 3 or less, it is not very effective. Products using modified PVA copolymerized with long-chain alkyl groups also slightly improve the storage stability of aqueous solutions, but they tend to gel and are problematic in handling. On the other hand, an aqueous solution using a PVA-based polymer having a long chain alkyl group having 4 or more carbon atoms at the end has little change in viscosity over time and is fluid and easy to handle.

[Table] Example 3 As Invention Example 7, the degree of polymerization was 1750 and the degree of saponification was 88.5.
Mol% PVA (Kuraray Poval PVA-217) 62
Department, Chemical Starch Co-Film 8.0 (Oji National Co., Ltd.)
PVA with a long chain alkyl group at the end of 35 parts
Three parts of the polymer (P-6) were added, and this mixture was poured into water and dissolved by heating at 95°C for 2 hours to prepare an aqueous solution with a concentration of 10%, and the transmittance of this aqueous solution at 20°C was measured. . As Example 8 of the present invention, 62 parts of PVA-217 and 35 parts of chemically engineered starch Petrosize L-2B (manufactured by Nippon Star Chemical Co., Ltd.) were mixed with PVA-217 and 35 parts of PVA-217.
An aqueous solution containing 3 parts of -6 was prepared in the same manner, and the transmittance was measured. As Comparative Example 6, a 10% aqueous solution containing 62 parts of PVA-217 and 35 parts of Cofilm 80 was prepared, and the transmittance at 20°C was measured. In addition, as Comparative Example 7, 62 parts of PVA-217 and Petrosize L-2B were used.
An aqueous solution of 35 parts was similarly prepared and the transmittance was measured. Also, as Comparative Example 8,
62 parts of PVA-217 and 35 parts of Cofilm 80 were copolymerized with 0.6 mol% lauryl vinyl ether.
An aqueous solution containing 3 parts of long-chain alkyl group copolymerized modified PVA (PVA-L) with a degree of polymerization of 700 and a degree of saponification of 98.6 mol % was prepared in the same manner as in Example 7, and the transmittance was measured. The results are shown in Table-5. The aqueous solution containing a PVA-based polymer having a long-chain alkyl group at the end had a higher transmittance than the aqueous solution consisting only of PVA-217 and modified starch, indicating improved compatibility. It can also be seen that PVA copolymerized with long-chain alkyl groups has little effect on improving compatibility with these modified starches.

[Table] * Method for measuring transmittance of aqueous solution Hitachi spectrophotometer (manufactured by Hitachi, Ltd.) used Wavelength: 650 nm Cell width: 10 mm Example 4 As Invention Example 9, the degree of polymerization was 1750 and the degree of saponification was 98.5.
A PVA polymer having a long chain alkyl group at the end is added to a 7:3 (by weight) mixture of mol% PVA (Kuraray Poval PVA-117) and oxidized starch Mermaid M-200 (manufactured by Shikishima Starch Co., Ltd.). (P-2) was added and dissolved in hot water at 95°C to prepare an aqueous solution with a concentration of 10%. The system containing a PVA polymer having a long chain alkyl group at the end has better transparency and better compatibility than an aqueous solution consisting only of oxidized starch and PVA-117. This is shown by the transmittance (solid line 1) in FIG. As Comparative Example 9, PVA with a polymerization degree of 550 and a saponification degree of 98.5 mol% (PVA
The transmittance of an aqueous solution using (-105) is shown in FIG. 2 (dotted chain line in 3), and the transmittance hardly changes, indicating that the compatibility is poor. As Comparative Example 10, 0.6 mol% of uryl vinyl ether was copolymerized instead of the PVA polymer (P-2) having a long chain alkyl group at the end of Invention Example 9, with a degree of polymerization of 700 and a degree of saponification of 98.6 mol. % of long-chain alkyl group copolymer-modified PVA (PVA-L), the transmittance was measured in the same manner as in Inventive Example 9. The results are shown in Figure 2 (dotted line in 2), and the compatibility with oxidized starch is better than that of PVA-105, but the system in which a PVA-based polymer having a long-chain alkyl group at the end of Invention Example 9 is added. It is inferior to * Transmittance measurement method for aqueous solution Hitachi spectrophotometer (manufactured by Hitachi Seisakusho Co., Ltd.) was used. Wavelength: 650 nm, cell width: 10 mm. Example 5 As Inventive Example 10, the degree of polymerization was 1750 and the degree of saponification was 88.5.
Mol% PVA (Kuraray Poval PVA-217) 62
Department, oxidized starch co-film 80 (Oji National Co., Ltd.)
35 parts of (manufactured by) have a long chain alkyl group at the end.
Three parts of PVA-based polymer (P-3) were added, and the mixture was poured into water and dissolved by heating at 95° C. for 1 hour to prepare an aqueous solution with a concentration of 10%. Using this aqueous solution, a film was formed on a drum set at 70°C, and the film was conditioned for one week at 20°C and 65% RH, and then the strength and elongation of the film was measured. Inventive Example 11 also includes 62 parts of PVA-217, 35 parts of oxidized starch Mermaid M-200 (manufactured by Shikishima Starch Co., Ltd.), and 3 parts of P-3.
The strength and elongation of the film was measured in the same manner. Comparative Example 11 was made by adding 35 parts of Corfilm 80 to 62 parts of PVA-217, and Comparative Example 12 was made by adding PVA-217 to 35 parts.
Comparative Example 13 was prepared by adding 62 parts of 217 and 35 parts of Mermaid M-200, and as Comparative Example 13, 62 parts of PVA-217, 35 parts of Corfilm 80 and lauryl vinyl ether were added.
Long-chain alkyl group copolymerized modified PVA (PVA-
L), the strength and elongation of the film was measured in the same manner as in Inventive Example 10. The results are shown in Table 6, and the film obtained by adding a PVA polymer having a long chain alkyl group at the end of one example of the present invention has higher strength and elongation than the film without the addition. Indicates the physical properties of the film. Further, when the film of the present invention is closely observed with an optical microscope, it is observed that the oxidized starch is more finely dispersed and uniformly dispersed than that of the comparative example. In this way, in terms of film properties, PVA polymers with long chain alkyl groups at the terminals have better compatibility with starch than modified PVA copolymerized with long chain alkyl groups, and therefore have better film properties. It can be seen that it is.

[Table] * Measuring method of film physical properties Shimadzu Autograph DCS-100 model (manufactured by Shimadzu Corporation)
Sample used: width 15 mm, thickness approximately 60 μm, measurement length 50 mm, tensile speed 500 mm/min

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the content of the PVA-based polymer in a PVA-based polymer and cornstarch mixture and the viscosity of the aqueous solution. In the figure, X represents the content (wt%) of the PVA polymer based on the total solid content, and Y represents the viscosity of the aqueous solution measured by a B-type viscometer at 20°C. FIG. 2 is a diagram showing the relationship between the content of the PVA-based polymer in a mixture of PVA-based polymer and oxidized starch and the transmittance of an aqueous solution. In the figure, X represents the content (wt%) of the PVA polymer in the total solid content, and Y represents the transmittance of the aqueous solution at 20°C.

Claims (1)

[Scope of Claims] 1. A starch-based polymer composition comprising starch (A), a polyvinyl alcohol-based polymer (B) having a long-chain alkyl group having 4 to 50 carbon atoms at the end, and polyvinyl alcohol (C). 2 The mixing ratio of (A) and [(B) + (C)] is 2 to 10,000 parts by weight of [(B) + (C)] to 100 parts by weight of (A), and (C)
is 1 to 10,000 parts by weight per 100 parts by weight of (B), and (A)
The starch-based polymer composition according to claim 1, wherein (B) is present in an amount of 1 to 3000 parts by weight per 100 parts by weight.