JPS6241249B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vinyl chloride resin composition having water-absorbing and swelling properties and comprising a vinyl chloride resin and a saponified starch-acrylonitrile copolymer.

At present, natural rubber, synthetic rubber, and partly vinyl chloride resin are used as packing materials for the joints of humid pipes used in sewerage systems and the like. However, these packing materials tend to deteriorate easily, and not only do they cause water leakage from the joints due to damage, but they can also cause underground water leakage.
Rainwater intrudes, increasing the amount of water treated at water treatment plants,
Processing capacity was often exceeded.

The inventors of the present invention have conducted intensive studies on methods to prevent water from leaking from sewer pipes, etc., and to prevent groundwater from flowing back into the pipe, and have found that a film made of saponified starch-acrylonitrile copolymer is used as a packing material for the joint of the pipe. They found that when used, they expanded on contact with water and had the effect of making the joints tighter, but these films were too thin and did not have a sufficient packing effect, and the film was formed using a starch-acrylonitrile copolymer. A special method must be used in which the saponified combined product is once dissolved in a solvent and then cast, and furthermore, saponified starch-acrylonitrile copolymer alone has low strength and poor durability. The present inventors further found that when a composition obtained by mixing a saponified starch-acrylonitrile copolymer with a vinyl chloride resin was molded using a normal thermoplastic resin molding method and brought into contact with water, the starch-acrylonitrile copolymer was mixed with water. It was found that the composition exhibited large expansibility similar to that of a saponified polymer, and it was also found that the composition had excellent strength and durability without impairing the properties of vinyl chloride resin. Then, when the composition was used as a packing material, it was found that it exhibited an extremely high sealing effect, and there was no leakage of water from the humid pipe, and there was no backflow of underground water, etc., and the present invention was achieved.

That is, an object of the present invention is to provide a vinyl chloride resin composition having water absorption and expansion properties suitable for use as packing materials, joint materials, etc. This can also be achieved with a vinyl chloride resin composition comprising 100 parts by weight of resin and 2 to 300 parts by weight of saponified starch-acrylonitrile copolymer.

To explain the present invention in detail, the vinyl chloride resin used in the present invention can be produced by suspension polymerization, emulsion polymerization,
It may be produced by any polymerization method such as bulk polymerization or solution polymerization, and it may be made of not only vinyl chloride homopolymer, but also comonomers containing vinyl chloride as a main component and copolymerizable therewith, such as ethylene, Examples include binary copolymers and ternary copolymers with propylene, vinyl acetate, vinyl methyl ether, acrylic acid, methyl acrylate, styrene, vinylidene chloride, methyl methacrylate, etc., and the structure of these copolymers. It is not particularly limited, and may be a random copolymer, a block copolymer, or a graft copolymer.
Furthermore, the vinyl chloride resin of the present invention can be used as a mixture of the above-mentioned vinyl chloride homopolymer and copolymer, or as a mixture with other thermoplastic resins mainly composed of vinyl chloride resin, such as polystyrene, ABS resin, etc. It is also possible.

The saponified starch-acrylonitrile copolymer used in the composition of the present invention is obtained by graft copolymerizing an acrylonitrile compound onto starch such as wheat starch, rice starch, or corn starch, and then applying the resulting graft copolymer to starch in the presence of an alkali. It is a saponified product, and its chemical structure consists of a graft copolymer with starch as the backbone and a copolymer of acrylic acid or its alkali salt and acrylamide as branches. Acrylonitrile compounds include not only acrylonitrile but also the α-position or β-position of the double bond, such as methacrylonitrile.
It may have a substituent such as an alkyl group or an aryl group at the - position. A typical method for producing a saponified starch-acrylonitrile copolymer is carried out by General Mills Chemical Co., for example, by heating a 5 to 10% by weight starch aqueous solution to form a paste, and then cooling it. A starch-acrylonitrile copolymer is produced by adding and stirring an acrylonitrile compound in a range of 0.2 to 15 moles, preferably 0.5 to 10 moles per mole of starch structural units in the presence of a cerium catalyst, and adding alkali metal water to this copolymer. An oxide is added and saponified by heating, followed by purification, separation and drying. Therefore, in the saponified product of starch-acrylonitrile copolymer, the molar ratio of acrylic acid or its alkali metal salt to acrylamide contained therein is in the range of 1:0.1 to 10, preferably 1:0.5 to 2. is preferably used. Of course, the saponified starch-acrylonitrile copolymer is a graft copolymer whose branches are a copolymer of a polymerizable monomer having a carboxyl group or an alkali metal salt thereof and a polymerizable monomer having an acid amide group. If so, the manufacturing method is not particularly limited.

The present invention resides in a vinyl chloride resin composition containing a vinyl chloride resin as described above and a saponified starch-acrylonitrile copolymer. The blending amount of the saponified starch-acrylonitrile copolymer is preferably in the range of 2 to 300 parts by weight, preferably 50 to 200 parts by weight, based on 100 parts by weight of the vinyl chloride resin. If the amount is less than 2 parts by weight, the properties will be close to those of vinyl chloride resin, and the water absorption and swelling properties will be low, and if it is more than 300 parts by weight, the desirable physical properties of vinyl chloride resin will be likely to be impaired.

Specifically, the composition of the present invention is manufactured as follows. For example, after uniformly mixing 25 to 350 parts by weight of a plasticizer such as dioctyl phthalate or dioctyl adipate to 100 parts by weight of vinyl chloride resin in a substantially water-free state, starch-acrylonitrile copolymer A vinyl chloride resin composition is obtained by uniformly mixing saponified powder with a Henschel mixer, ribbon blender, Banbury mixer, etc., but this composition is usually heated and kneaded with a kneading machine such as an extruder or roll mill to form pellets. It is often done. "Substantially water-free state" means that water is not necessarily added to the vinyl chloride resin and the saponified starch-acrylonitrile copolymer, and they are used in the form of granules or powder. In the kneaded vinyl chloride resin composition, saponified starch-acrylonitrile copolymer powder is uniformly dispersed in the vinyl chloride resin and is coated with the vinyl chloride resin. Although the composition of the present invention does not particularly require a plasticizer for the vinyl chloride resin, it is preferable that the vinyl chloride resin itself has flexibility when used for packing materials, etc., so it is usually added with a plasticizer. is used. In addition, before adding the saponified starch-acrylonitrile copolymer, the composition of the present invention may contain conventional additives used for vinyl chloride resins, such as lead, tin, barium, cadmium, calcium, zinc, magnesium, etc. Up to 30 parts by weight of stabilizers such as metal stabilizers, epoxy stabilizers, and antioxidants, and lubricants such as fatty acids, silicones, polyhydric alcohols, polyglycols, amides, amines, fatty acid esters, and waxes. Fillers such as calcium carbonate, diatomaceous earth, silica, clay, etc. may be added in an amount of up to 5 parts by weight, and up to 100 parts by weight (all based on 100 parts by weight of the vinyl chloride resin).

The compositions of the invention may also be prepared in the presence of water. That is, it is produced by uniformly mixing an aqueous dispersion or emulsion of a vinyl chloride resin with a water-swollen liquid or an aqueous solution of a saponified starch-acrylonitrile copolymer.

The composition of the present invention may be a water-free composition, an aqueous dispersion, or an aqueous emulsion, depending on the intended use, but water may be present if the composition is easy to handle or can be molded using various methods. Vinyl chloride resin compositions that do not contain the above-mentioned properties have higher utility value.

When the vinyl chloride resin composition of the present invention is used, for example, as a packing material for a humid pipe, in the case of a water-free composition, ordinary vinyl chloride resin molding methods are used, such as extrusion molding, calendering, pressing, etc. A sheet or film is produced by molding or the like, and the sheet or film is punched or cut out according to the size of the hume tube to make a packing material, or a packing material is directly produced by injection molding. As the molding temperature, the molding temperature of vinyl chloride resin is used as is. On the other hand, in order to obtain a packing material from a vinyl chloride resin composition in the form of an aqueous dispersion or an aqueous emulsion, the composition is cast and dried to produce a film, or the composition is coated on a synthetic resin film, sheet, fabric, etc. However, there are methods such as punching or cutting out these materials to make packing materials.

The vinyl chloride resin composition of the present invention exhibits extremely high water absorption and swelling properties when immersed in water, even though most of the saponified starch-acrylonitrile copolymer is covered with vinyl chloride resin. It fully demonstrates the characteristics of vinyl chloride resin, and has extremely high utility value as a packing material, joint material, etc.

When the composition of the present invention is used as a packing material, it absorbs water and expands over time, and the packing material does not shrink in volume. Normally, vinyl chloride resin mixed with water-absorbing methylcellulose, gelatin, polyvinyl alcohol, casein, etc. generally has low water absorption, and even if it expands once it absorbs water, it will shrink in volume over time and cause packing. It cannot be used as a material. Of course, the composition of the present invention does not prevent the mixing of these water-absorbing substances.

Next, the composition of the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples unless it departs from the gist thereof.

Example 100 parts by weight of vinyl chloride resin (average degree of polymerization 1400, homopolymer), 70 parts by weight of dioctyl phthalate, 5 parts by weight of tribasic lead sulfate, 0.5 parts by weight of stearic acid.
Parts by weight were uniformly stirred with a Henschel mixer, and 100 parts by weight and 200 parts by weight of saponified starch-acrylonitrile graft copolymer (manufactured by General Mills Chemical Co., USA, trade name SGP) were added as water-absorbing and swelling substances. and mixed uniformly (Examples 1 and 2). The composition is rolled in a roll mill.
After kneading at 150°C for 7 minutes to a thickness of 0.3mm, it was taken out as a 0.7mm thick sheet and press-formed in a press molding machine for 5 minutes at a temperature of 170°C and a press pressure of 210Kg/cm ² to a thickness of 2.
A sheet of mm was prepared and used as a test piece.

When the test piece was immersed in water (tap water) at 20°C for a predetermined number of days, it expanded three-dimensionally. This water absorption swelling property was expressed as a linear expansion coefficient and is shown in the drawing.

For comparison, a vinyl chloride resin composition to which 100 parts by weight of other water-absorbing and swelling substances methyl cellulose, gelatin, polyvinyl alcohol, and casein were added was also tested in the same manner as in Example 1, and the results are also shown in the drawings. .

The drawing is a graph showing the swelling property changing over time, where the horizontal axis shows the number of days of immersion and the vertical axis shows the linear expansion rate. In the figure, 1 and 2 are the compositions of Examples 1 and 2,
3, 4, 5 and 6 are respectively methylcellulose,
A composition with added gelatin, polyvinyl alcohol and casein is shown.

As is clear from the drawings, in the composition of Example 1, the thickness of the sheet increased by 1.4 times in 45 to 60 days;
The composition of Example 2 doubles in thickness in about 15 days, and the thickness does not decrease (there is no volumetric shrinkage). On the other hand, in compositions containing water-absorbing substances other than those of the present invention, although an increase in wall thickness is observed, the volume shrinks when immersed for a long period of time, and therefore cannot be used as a durable packing material. It turns out that you can't get it.

[Brief explanation of the drawing]

The drawing is a graph showing the change over time in the water absorption expansion rate of the vinyl chloride resin composition of the present invention, where the horizontal axis shows the number of days of water immersion and the vertical axis shows the linear expansion rate. In the figure, 1 and 2 are the compositions of the present invention, 3, 4, 5
and 6 show compositions of comparative examples.

Claims (1)

[Claims] 1. A vinyl chloride resin composition comprising 100 parts by weight of a vinyl chloride resin and 2 to 300 parts by weight of a saponified starch-acrylonitrile copolymer.