JPS5929612B2 - Water-absorbing/hygroscopic thermoplastic resin moldings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a molded article that improves water absorption and hygroscopicity, which are the drawbacks of hydrophobic thermoplastic resins. ) A thermoplastic resin molded product having water absorbing and hygroscopic properties obtained by melt-molding the mixture with heat-melting polyvinyl alcohol containing 15 to 70 mol% of residual acetic acid groups at a weight ratio of 90:10 to 40:60. It is.

Conventionally, polyvinyl alcohol (hereinafter abbreviated as PVA) has been used.

) is well known as a resin with high water absorption, and attempts have been made to use PVA to improve the water absorption and hygroscopicity of hydrophobic thermoplastic resins. For example, the Special Public Interest Publication No. 44-2086
No. 9 proposes a method of melt-mixing hydrophobic thermoplastic resin with water-containing PVA using water as a PVA plasticizer, and Japanese Patent Publication No. 48-3700 proposes a method of melting and mixing finely powdered PVA with melting heat. A method of dispersing and mixing plastic resins has been proposed. However, since the former uses water-containing PVA, when molded at a high temperature of 100°C or higher, foaming occurs due to boiling of water, and water is a non-plasticizer for hydrophobic resins, which poses an obstacle to uniform mixing.

However, since the latter method involves mixing anhydrous, non-heat-melted PVA fine powder with a molten thermoplastic resin, it not only limits the particle size but also has the disadvantage that the surface of the resulting molded product becomes uneven. In this way, since conventionally known PVA does not melt under heat, it was necessary to mix it with hydrophobic thermoplastic resin under special conditions. However, as a result of research on heat-melting PVA that can be mixed and melted with various general-purpose hydrophobic thermoplastic resins, the average degree of polymerization is 50-300, and the residual acetate group is 15-300.
The present invention was completed by discovering that 70 mol PVA is heat-meltable and has water absorption and moisture absorption ability.

That is, the present invention is a molded product obtained by melt-molding a specific amount of a hydrophobic thermoplastic resin mixed with a specific amount of a new heat-melting PVA having an average degree of polymerization of 50 to 300) and a residual acetic acid group of 15 to 70 mol%. The molded product is not only of excellent quality that could not be obtained by conventional mixing and melting of non-melting PVA and thermoplastic resin, but also industrially stable and easily manufactured.

The present invention will be explained in detail.

In the present invention, the PVA mixed with the hydrophobic thermoplastic resin is 140
It is a partially saponified product that melts at ~200°C, has an average degree of polymerization of 50 to 300, and has a residual acetate group of 15 to 70 mol%.

In particular, when a material that swells in water but does not completely dissolve in water is required, a material containing 40 to 70 mol % of residual acetic acid groups may be used. These heat-melting PVAs are usually suitably used in the form of powder, chips or pellets. PV
If the average degree of polymerization of A exceeds 300, the melt temperature and melt viscosity will increase, making it difficult to mix with the thermoplastic resin, so it is desirable that the average degree of polymerization is 300 or less.

On the other hand, if the degree of polymerization is extremely low below 50, thermal decomposition occurs and melt molding is difficult, so for these reasons, the average degree of polymerization of PVA is suitably in the range of 50 to 300. If the residual acetate group in PVA exceeds 70 moles, the water swelling property will decrease, and even if mixed with a thermoplastic resin, it will not be able to impart sufficient hygroscopicity and water absorption, so it is unsuitable. If it is less than that, the partially saponified PVA will not be thermally melted and is therefore unsuitable.

In addition, since PVA with 15 to 40 mol% of residual acetate groups easily dissolves in cold water, thermoplastic resin molded products made by mixing this PVA can be used for purposes that do not come into contact with water for a long time, or if the molded product is intentionally removed from PVA. It is used for purposes such as elution and utilization. The thermoplastic resin used in the present invention includes hydrophobic polyolefins such as polyethylene, polypropylene, poly3-methyl-1-butene, poly4-methyl-1-butene,
Benzene, poly-4-methyl-1-hexene, poly-5-methyl-1-hexene, poly-4,4-dimethyl-1-benzene, polymers of styrene or its derivatives, or general-purpose thermoplastic resins, Examples include butyral resin, acetal resin, fluororesin, vinyl chloride and vinylidene chloride resin, nylon resin, polyester resin, and the like.

The present invention is formed by melt-mixing a mixture of these heat-melting PVA and a hydrophobic thermoplastic resin using a suitable blender at a heating temperature of 130 to 300°C.

Since the melt mixing is carried out with both the PVA and the thermoplastic resin in a molten state, they can be blended uniformly in a short time. The resin may be molded after blending or while blending a certain amount at a time. The appropriate mixing ratio of hot-melt PVA and hydrophobic thermoplastic resin is in the range of 10/90 to 60/40 by weight.

If the mixing ratio of hot-melt PVA is reduced to less than 10/90 by weight, the desired effect of improving water absorption and hygroscopicity will decrease, and if it is increased from 60/40, the mechanical performance of the molded product will deteriorate. Therefore, it is undesirable. The thermoplastic resin molded product having water absorbing properties and hygroscopic properties of the present invention can be made of calcium carbonate if hardness of the molded product or surface roughness is required as long as it does not impair its water absorbing properties or hygroscopic properties. Water-insoluble inorganic salts such as magnesium sulfate, titanium oxide, tin oxide, clay, or one or two metal oxides
In some cases, molding is done by mixing an appropriate amount of powder or more with the two raw material polymers, and if coloring is required, pigments are added, and if light and heat stability are required, stabilizers are added. Needless to say, molding may be carried out by adding and blending each of these.

Further, if necessary, a plasticizer for a hydrophobic thermoplastic resin may be added and melt-molded. The present invention is a thermoplastic resin molded product having water absorbing and hygroscopic properties, and since the molded product is melt-molded, conventionally known fibers, films, molded products, etc. can be melted and applied to the surface of the molded product. It can replace almost all uses of conventional melt-molded thermoplastic injection resins, such as coating.

Next, in order to show an example of the effect of the present invention, the average degree of polymerization 1
40 and the remaining acetate group is 42 moles? PVA and polyethylene (PE), polypropylene (PP), polystyrene (P
A sample with a thickness of 2 to 3 mm was made by molding a resin obtained by melting and mixing St), and the tensile strength, elongation, and water absorption were measured, and the results are shown in Table 1 in comparison with a molded product without PVA mixed. Ta.

PE: Polyethylene resin with average molecular weight 38,0001, specific gravity 0.939, melting point 115-118°C PP: Polypropylene resin PS with average molecular weight 70,0001, melting point 165°C
t: Polystyrene resin with average molecular weight 100,0001 and deformation temperature 86°C PVA: Average degree of polymerization 140, residual acetic acid group 4
Polyvinyl alcohol resin with 2 mol% and melting point of 157°C Tensile strength: Measured according to ASTM D638 Water absorption rate (24 hours): Measured according to ASTM D57O As is clear from Table 1, heat-melting PVA is uniformly mixed into hydrophobic thermoplastic resin. It is clear that by melt-mixing the molded article, the water absorption rate can be significantly increased without reducing the tensile strength of the single molded article.

It goes without saying that the molded product of the present invention may be subjected to cold stretching, hot stretching, or heat treatment as necessary.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 90 parts by weight of polyethylene (average molecular weight 38,000, specific gravity 0.939, melting point 115-1180C), average degree of polymerization 140, residual acetic acid group 42 mol%, melting point 15
Mix parts by weight of PVAlO at 7°C with a chip,
The mixture was uniformly melted and mixed at 80°C.

The mixed resin thus obtained was molded into a test piece with a thickness of 3 mTL. The tensile strength of this test piece according to ASTM-D638 is 185 kg/(1-J Mo V1, elongation is 190
%, and the water absorption rate (24 hours) was 2.3%. On the other hand, a PE resin molded product that does not contain PVA has a tensile strength of 180 kg/01? L1 elongation 195%, water absorption rate (2
4 hours) was only 0.01%. Example 2 Polypropylene (average molecular weight 70,000, melting point 165°C
) 70 parts by weight of resin, average degree of polymerization 60, residual acetic acid group 57
Mol%, 30 parts by weight of PVA resin with melting point 145°C added, 1
The mixture was melted at 80° C. and mixed uniformly.

This mixed resin was molded into a test piece with a thickness of about 2 mm in the same manner as in Example 1, and the water absorption rate was measured, and it was found to be 47%. In contrast, the water absorption rate of the molded article made of polypropylene resin alone was 0.01%. There was no significant difference in other mechanical performance. Example 3 To 60 parts by weight of polystyrene resin (average molecular weight 100,000, deformation temperature 86°C) was added parts by weight of PVA4O having an average degree of polymerization of 258, residual acetic acid groups 64 mol%, and a melting point of 172°C.
The mixture was melted at 230°C and mixed uniformly.

This mixed resin was molded into a 3 mm thick test piece in the same manner as in Example 1, and its tensile strength and elongation were measured. Tensile strength is 392kg/Cdl elongation is 2.4? It was hot.
Its water absorption rate is 4.0%, whereas a molded product made of polystyrene alone has a tensile strength of 415 kg/CTiL elongation of 2.1.
, the water absorption rate was 0.03%. Example 4, Comparative Examples 1 to 4 Polypropylene (average molecular weight 70,000, melting point 165
20 parts by weight of each of the five types of PVA shown in Table 2 were added to 80 parts by weight (20 parts by weight) of each of the five types of PVA shown in Table 2, melted and mixed at 200°C, and after observing the mixing state, the mixture was mixed in the same manner as in Example 1 to a thickness of approximately 2m
A test piece of m was molded and the water absorption rate (24 hours) was measured.

The results were as shown in Table 2. As is clear from Table 2, if the degree of polymerization is too low (Comparative Example 3) or the residual acetic acid group is too high (Comparative Example 2), the melt viscosity of PVA will be too low, resulting in poor mixability. .

On the other hand, if the degree of polymerization is too high (Comparative Example 4), the melt viscosity is high, and if the residual acetate group is too low (Comparative Example 1), P
Decomposition of VA occurs and miscibility deteriorates in both cases. Example 5, Comparative Example 5 Polypropylene (average molecular weight 70,000, melting point 165
°C) 80 parts by weight, average degree of polymerization 2801 residual acetic acid group 62
Add 20 parts by weight of PVA with mol% and melting point of 172°C,
It was melted at 0°C and mixed uniformly.

This mixed resin was molded into a test piece with a thickness of about 211 cm in the same manner as in Example 1. The surface of the molded product obtained is smooth,
It was found that PVA was mixed uniformly. Also,
When the surface was immersed in water at 30° C. and visually inspected for wetness, it was found to be uniformly wet without any water droplets. and,
The water absorption rate (24 hours) was 3.8%. For comparison, PVA was used with an average degree of polymerization of 550 and a residual acetic acid group of 12 mol%.
A molded article was obtained in the same manner as in Example 4, except that PVA (saponification degree: 88 mol%) was used.

It was found that the surface of the obtained molded product was rough, and water beads formed in some areas when immersed in water, indicating that the PVA was mixed non-uniformly. Moreover, the water absorption rate (24 hours) was 0.8%. The tensile strength of this molded article was 70% lower than that of Example 4. Example 6, Comparative Example 6 Polypropylene (average molecular weight 70,000, melting point 165
℃) 80 parts by weight of PVA with an average degree of polymerization of 65, residual acetic acid group 10 mol%, melting point of 185℃, melt viscosity cannot be measured (due to thermal decomposition) as A, and as B with an average degree of polymerization of 65
is the same as, but the remaining acetate group is 20 moles? , melting point 155
Using PVA with a melt viscosity of 1000 poise at 200 °C and 200 °C, 20 parts by weight of each was mixed with the above polypropylene,
Melt mixing was carried out at 190°C.

As a result, thermal decomposition occurred in AOI (PVA) and it was not possible to mix uniformly. However, BO)PVA was mixed homogeneously. Approximately 2g thick molded using this material
When the water absorption rate (24 hours) of the test piece of B (7) was measured, it was 0.01% for polypropylene alone;
When 20 parts by weight of PVA was uniformly mixed, the content was 4.0%. Example 7 100 parts by weight of polyvinyl chloride with an average degree of polymerization of 1,300, 50 parts by weight of dioctyl phthalate, 2 parts by weight of dibutyltin laurate, and 0 parts by weight of barium stearate as plasticizers.
．． 4 parts by weight were blended, uniformly melted and mixed at 180°C, and molded into a test piece with a thickness of about 2 mm.

The tensile strength of this molded product is 1601<fl/CTL. The elongation was 350% and the water absorption rate (24 hours) was 0.7%. On the other hand, the average degree of polymerization is 220, and the residual acetic acid group is 68 moles? Parts by weight of PVA2O were uniformly mixed with the above formulation at 180°C and then molded in the same manner. The properties of the test piece obtained were tensile strength of 152 kg/Crill elongation of 320%, and water absorption rate (24 hours) of 2.3. It was %.

Example 8 Polyethylene terephthalate (hereinafter abbreviated as PET) has an average molecular weight of about 10,000 and an intrinsic viscosity of 0.6 as measured using a mixed solution of phenol/tetrachloroethane=60/40 (parts by weight).

), 10 parts by weight of PVA with an average degree of polymerization of 290 and residual acetic acid groups of 42 mol % was added, mixed uniformly at 280°C, and molded into a test piece with a thickness of about 2 mm in the same manner as in Example 1. However, when the water absorption rate (24 hours) was measured, it was 2.4%. On the other hand, the water absorption rate (24 hours) of the molded product made of PET alone was 0.15%. There was no significant difference in mechanical properties between the two. Example 9 Average molecular weight 17,500,
Polycaprolactam 80 with relative viscosity 2.6 in 98% sulfuric acid
P with an average degree of polymerization of 140 and a residual acetic acid group of 35 mol% in weight parts
20 parts by weight of VA was added and uniformly melted and mixed at 250° C., and a test piece having a thickness of about 2 m and 71 L was prepared in the same manner as in Example 1.

The tensile strength of polycaprolactam alone test piece is 750
kg/Cdl elongation is 230%, water absorption rate (24 hours) is 1
．． It was 6%. On the other hand, when 10 parts by weight of PVA is added, the tensile strength is 730 kg/C! Ill growth is 21
0%, and the water absorption rate (24 hours) was 4.9%. Example 10 30 parts by weight of triethylene glycol di-2-ethyl butyrate was blended with 100 parts by weight of a butyral resin having an average degree of polymerization of 1,300 and a degree of butyralization of 65 mol %, and molded.

On the other hand, this compound had an average degree of polymerization of 230 and a residual acetate group of 40.
Add 25 parts by weight of PVA with mol% and melting point of 162°C, and add 1
The mixture was melt-mixed at 70°C and molded. The water absorption rate (24 hours) of the molded products obtained was 1.1% for the former and 4.3% for the latter. Example 11 To 80 parts by weight of acetal resin (a copolymer of trioxymethylene and ethylene oxide), 20 parts by weight of PVA having an average degree of polymerization of 166, residual acetic acid groups of 62 mol%, and a melting point of 158°C was added, and the mixture was melt-mixed at 190°C. Then, it was molded in the same manner as in Example 1.

The performance of the obtained molded product with a thickness of about 2 mm is that the acetal resin alone has a tensile strength of 560 kg/d), an elongation of 75%, and a water absorption rate (
24 hours) was 0.22%, whereas the one containing PVA had a tensile strength of 540 kg/Cli! L) Elongation was 70% and water absorption rate (24 hours) was 2.9%. Example 12 80 parts by weight of polychlorotrifluoroethylene with a melting point of 210°C was blended with 20 parts by weight of PVA with an average degree of polymerization of 230, 35 mol% of residual acetic acid groups, and a melting point of 165°C, and melt-mixed at 230°C to produce an example. It was molded in the same manner as 1.

The water absorption rate (24 hours) of the obtained molded article was 1.8%. On the other hand, in the case of polychlorotrifluoroethylene alone, the water absorption rate (24 hours) was 0.01%. Example 13 6 parts by weight of diphenyl ethyl ether was added to 100 parts by weight of a polyvinylidene chloride resin copolymerized with 15 mol% of vinyl chloride units, and the mixture was uniformly melted and mixed at 170°C to form a resin with a thickness of about 2
It was molded into a test piece of mm.

This molded article had a tensile strength of 240 kg/CTit, an elongation of 210%, and a water absorption rate (24 hours) of 0.1%.
On the other hand, the tensile strength of a molded article prepared by homogeneously mixing PVA2O with an average degree of polymerization of 220) and 68 mol% of residual acetate groups at 170°C was 235I (g/CTil.
The elongation was 220% and the water absorption rate (24 hours) was 2.3%.

Claims (1)

[Claims] 1 A water-absorbing product made by mixing a hydrophobic thermoplastic resin and heat-melting polyvinyl alcohol having an average degree of polymerization of 50 to 300 and a residual acetic acid group of 15 to 70 mol% in a weight ratio of 90:10 to 40:60, and melt-molding the mixture. A thermoplastic resin molded product that has moisture and moisture absorption properties.