JPH0657759B2 - Manufacturing method of soft vinyl chloride foam moldings with small permanent set - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a foam molding comprising a specific soft vinyl chloride resin composition having a foaming ratio of 1.2 to 2.5 and a small permanent set. The manufacturing method of goods.

[Prior Art] Conventionally, a so-called soft vinyl chloride resin composition obtained by adding a plasticizer to a vinyl chloride resin for the purpose of reducing the weight of a soft vinyl chloride product and improving sound insulation, heat insulation and sealing properties. Although the foamed molded product from is manufactured and used, it has dense and uniform independent foamed cells, and the expansion ratio is
A flexible vinyl chloride foamed molded product that is 1.2 times or more and has a small permanent set has not been obtained, and is used only in a limited range.

As a method for producing a vinyl chloride-based foam molded article, there are an extrusion foam molding method, an injection molding method, a calender molding method, and the like, and a method of manufacturing using an evaporation type foaming agent and a decomposition type foaming agent. There is a manufacturing method.

The method of producing by using the decomposition type foaming agent by the extrusion foaming molding method has the advantage that it can be diverted by slightly modifying the conventionally used extruder and has the advantage that the process is simple. It is often used in the production of medium-foam molded products. In particular, in the field of this extrusion foam molding method, in addition to the permanent set, the expansion ratio, the uniformity of the foam cells, the extrusion shape is stable, and the molded product has a smooth surface and a good appearance. , Such foam-molded products have not been obtained.

Foaming ratio of such foamed molded product, uniformity of foamed cells,
When trying to solve problems such as moldability in extrusion molding, the addition of a processability improver is a generally adopted method, and it is well known that this method is effective to some extent. For example, as disclosed in JP-A-51-5371 and JP-A-58-52327, in the so-called two-stage foaming method in which a sheet is first molded and then foamed in a foaming furnace, Its effect has been recognized in terms of improving the expansion ratio of a molded product, the uniformity of foam cells, and the like. However, the effect is not recognized in general extrusion foam molding.

That is, in a general extrusion foam molding method, even if a commonly used copolymer containing methyl methacrylate as a main component and a processability improver having a specific viscosity of 1 to 2 is added, a dense and uniform independent foaming is performed. It is not possible to obtain a foamed molded product having cells and having a foaming ratio of 1.2 times or more and extremely excellent surface smoothness. In addition, even in the injection molding method, the specific viscosity is 1 to 2
With the addition of the processability-improving agent, a foamed molded product having a foaming ratio of 1.2 or more and having dense and uniform closed cells has not been obtained.

On the other hand, as disclosed in JP-A-61-66732, extrusion is performed by adding a decomposable foaming agent to a soft vinyl chloride resin composition containing a partially crosslinked acrylonitrile-butadiene rubber for the purpose of reducing permanent set. When foam molding is performed, the permanent set becomes small, but the problem that the expansion ratio is difficult to increase and uniform foam cells cannot be obtained becomes more prominent. For this reason, it is extremely difficult to obtain a foamed molded product having a compression set of 50% or less and a dense and uniform foam cell with a foaming ratio of 1.2 or more, only by adding the partially crosslinked acrylonitrile-butadiene rubber. .

[Problems to be Solved by the Invention] According to the present invention, when a flexible vinyl chloride resin composition foam-molded article is obtained by various foam-molding methods, the foaming state of the foam-molded article is dense and uniform according to the conventional technique. It is made to solve the problem that it is used only in a limited range because it is not possible to obtain a foamed molded product in which it is made into an independent foam cell state, the expansion ratio is 1.2 times or more, and the permanent set is small. It is a thing.

[Means for Solving Problems] The present invention is based on 100 parts by weight of a vinyl chloride resin (parts by weight, the same applies hereinafter) and methyl ethyl ketone (hereinafter referred to as MEK) in an amount of 5 to 90% (% by weight, the same applies below) Dissolvable acrylonitrile-butadiene rubber (hereinafter referred to as NBR) 5 to 150
Part, 0.4 g of a copolymer whose main component is methyl methacrylate
The specific viscosity of a 100 ml benzene solution containing
A molded product obtained by foam molding a soft vinyl chloride resin composition for foaming containing 1 to 60 parts of a methyl methacrylate copolymer of 2.5 or more, 20 to 200 parts of a plasticizer and 0.5 to 10 parts of a foaming agent. , A heat treatment at 40 to 120 ° C. for 20 minutes or more, and a method for producing a soft vinyl chloride foam molded article having a foaming ratio of 1.2 to 3.5 and a small permanent set.

[Examples] The vinyl chloride resin used in the present invention is a vinyl chloride resin obtained by homopolymerizing a vinyl chloride monomer or a vinyl chloride copolymer containing 85% or more vinyl chloride, and has a gel content of It may be a partially crosslinked vinyl chloride resin or the like, and any conventionally known vinyl chloride resin may be used as long as it complies with the above regulations.

Examples of the copolymer component other than vinyl chloride in the vinyl chloride copolymer containing 85% or more vinyl chloride include vinyl esters such as vinyl acetate and vinyl stearate, olefins such as ethylene and propylene, and (meth) acryl. Butyl acid, (meth) acrylic acid esters such as 2-ethylhexyl (meth) acrylate, maleic acid esters such as butyl maleate and octyl maleate, fumaric acid esters such as butyl fumarate and octyl fumarate, Alternatively, these acids and the like are exemplified,
It is not limited to these. Two or more of these components other than vinyl chloride may be used in combination.

As the partially crosslinked vinyl chloride resin containing a gel component, for example, a polyfunctional compound such as diallyl phthalate, diallyl maleate, polyethylene glycol di (meth) acrylate, or 1,2-polybutadiene is used as a crosslinking agent. Examples thereof include resins obtained by copolymerization, but are not limited to these.

Two or more of these vinyl chloride resins may be used in combination,
Further, the combination ratio can be freely selected according to the purpose.

The average degree of polymerization of the vinyl chloride resin is preferably 600 to 4500, and particularly preferably 1000 to 3200. When the average degree of polymerization is less than 600, it is difficult to dry up the plasticizer when it is mixed, and the permanent set of the molded article becomes large, which is not preferable. On the other hand, when the average degree of polymerization exceeds 4,500, it tends to be difficult to sufficiently gelate.

The NBR used in the present invention is a partially crosslinked NBR which dissolves in MEK in an amount of 5 to 90% (25 ° C), preferably 10 to 60%. M
The use of partially crosslinked NBR that dissolves in EK at 5 to 90% (25 ° C) can not only reduce the compression set of foam molded products and improve the restoring force after applying stress, but also foam molding At this time, the temperature dependence of the melt viscosity can be reduced, so that the temperature range during foam molding can be widened.

If the NBR is dissolved in MEK in an amount of more than 90%, the effect of reducing the compression set and the effect of reducing the temperature dependence during foam molding are unfavorable. Conversely, MEK
If it is dissolved in less than 5%, the moldability is lowered, which is not preferable.

In addition, dissolving in MEK means extracting with MEK at a temperature of 25 ° C. for 48 hours and passing through a 100-mesh filter.

The NBR used in the present invention is used in an amount of 5 to 150 parts, preferably 10 to 120 parts, per 100 parts of vinyl chloride resin. If the amount used is less than 5 parts, the effect of reducing the compression set is not sufficiently obtained, which is not preferable. On the contrary, if it exceeds 150 copies,
It is not preferable because the kneading property at the time of producing pellets becomes poor, the moldability at foam molding becomes poor, and the heat aging resistance, ozone resistance, weather resistance, etc. become poor.

The methyl methacrylate-based copolymer used in the present invention,
Mainly methyl methacrylate, ie 50-95%
It is a copolymer or graft copolymer of an acrylic acid ester and / or a methacrylic acid ester (excluding methyl methacrylate) and / or a small amount of a crosslinking agent contained therein.

The molecular weight of the methyl methacrylate copolymer is such that the specific viscosity of 100 ml of a benzene solution containing 0.4 g of the copolymer measured at 30 ° C. is 2.5 or more, preferably 2.5 to 6.0. And more preferably has a glass transition temperature
It is below 85 ℃. When the specific viscosity is less than 2.5, the uniformity and independence of cells of the foam-molded product, the surface smoothness of the extrusion-molded product, and the like are not improved, and the expansion ratio does not increase, which is not preferable. In addition, in order to improve the kneading properties during the production of pellet compounds, the glass transition temperature should be 85 ° C.
The following is preferable.

The methyl methacrylate copolymer used in the present invention is used in an amount of 1 to 60 parts per 100 parts of vinyl chloride resin. If the amount used is less than 1 part, a sufficient effect of improving the expansion ratio does not occur. On the contrary, if it exceeds 60 parts, the molded product becomes hard and inflexible, and the cost increases, which is not preferable. Two or more methyl methacrylate copolymers may be used in combination.

The plasticizer used in the present invention is added in order to give the molded article flexibility, rubber feel, and the like, and specific examples thereof include dibutyl phthalate, dioctyl phthalate, diisodecyl phthalate, diisononyl phthalate, diundecyl. Alkyl ester of aromatic polybasic acid such as phthalate, trioctyl trimellitate, triisooctyl trimellitate, dibutyl adipate,
Alkyl ester of aliphatic polybasic acid such as dioctyl adipate, diisononyl adipate, dibutyl azelate, dioctyl azelate, diisononyl azelate,
Examples include phosphoric acid alkyl esters such as tricresyl phosphate, and commonly used plasticizers such as polyester plasticizers, epoxy plasticizers and chlorinated paraffins. These may be used alone or in combination of two or more.

The plasticizer is used in an amount of 20 to 200 parts, preferably 30 to 160 parts, per 100 parts of vinyl chloride resin. If the amount used exceeds 200 parts, the heat distortion resistance of the molded product and the independence of the cells decrease,
On the other hand, if it is less than 20 parts, the molded product cannot be provided with flexibility, rubber feel, etc., which is not preferred.

Examples of the foaming agent used in the present invention include barium azodicarboxylate, hydrazodicarbonamide, azodicarbonamide, 4,4′-oxybisbenzenesulfonyl semicarbazide, N, N′-dimethyl-N, N′-diene. Nitrosoterephthalamide, N, N'-dinitrosopentamethylenetetramine, p-toluenesulfonyl hydrazide, benzene-1,3-disulfonylhydrazide, diphenylsulfone-3,3'-disulfonylhydrazide, p-
Examples include toluenesulfonyl semicarbazide.
These may be used alone or in combination of two or more kinds as appropriate.

The blowing agent is used in an amount of 0.5 to 10 parts, preferably 1.5 to 5 parts, per 100 parts of vinyl chloride resin. If the amount used is less than 0.5, the amount of gas generated is small and the expansion ratio does not increase, which is not preferable. On the contrary, when the amount used exceeds 10 times, over-foaming occurs and cell destruction and communication occur, resulting in cell uniformity,
Independence decreases, which is not preferable.

When producing a foam molded article by the method of the present invention, if necessary, stabilizer, lubricant, filler, ultraviolet absorber, pigment,
Rubbers (excluding partially cross-linked NBR), polycrethan resin,
Polyester resin, ethylene-vinyl acetate copolymer,
A thermoplastic resin such as chlorinated polyethylene may be blended and used, and further a kicking agent, a decomposition inhibitor, a foaming aid such as a cell regulator may be used. It may be appropriately selected according to

When producing a soft vinyl chloride-based foamed molded article by the method of the present invention, the components are blended and pelletized by using, for example, the step of producing a general soft vinyl chloride-based resin composition, and then the pellets are foamed and molded. Then, the molded product may be heat-treated.

That is, when blending, use a Henschel mixer,
Using a conventionally known blender such as a super mixer or ribbon blender, add the components such as vinyl chloride resin and then add the plasticizer all at once, intermittently or continuously.
The temperature is raised to ~ 150 ° C to dry up the plasticizer and produce a soft vinyl chloride resin powder compound.
At this time, the components other than the vinyl chloride resin may be added after the dry-up, or may be added during the dry-up.

Then, the mixture is supplied to a pressure kneader, a co-kneader, a mixing roll, various extruders and the like and kneaded at a temperature of 100 to 200 ° C. to produce a pellet compound of a soft vinyl chloride resin composition.

As the foam molding method, a conventionally used molding method such as an extrusion molding method, an injection molding method or a calender molding method can be used.

When molding by extrusion foam molding method, the pellet compound by extrusion foam molding method using various single-screw or twin-screw extruders with dies having various shapes according to the purpose of the molded product. A soft vinyl chloride foamed molded product is produced. During extrusion foam molding, it may be co-extruded with metal, soft PVC, hard PVC or the like.

The molding temperature in the extrusion foam molding method is usually in the range of 100 to 200 ° C., preferably, the temperature of the die is set lower than the temperature at the tip of the cylinder, and molding is preferably performed while maintaining this temperature difference at 5 ° C. or more. .

The shape of the screw is not particularly limited, and a conventionally known screw, such as a dullage type or a full flight type, may be used. The L / D of the screw is preferably from 15 to 40, more preferably from 15 to 30. The compression ratio of the screen is 1.0-
It is preferably 5.0, particularly preferably 1.5 to 3.5.

In this way, a foam-molded article with a foaming ratio of 1.2 to 2.5 times obtained by extrusion molding, injection molding, calendar molding, etc. and having dense and uniform independent foam cells is heat treated at 40 to 120 ° C for 20 minutes or more. When set, the permanent set is remarkably improved.
Up to now, there is no known method for significantly reducing the permanent set by heat treatment.

The heat treatment of the foamed molded product may be performed continuously or intermittently as long as it is heat-treated at 40 to 120 ° C for 20 minutes or more, and there is no particular limitation on the device, for example, hot air drying. It may be left standing in a heating furnace such as a machine or slowly moving in the heating furnace, but the temperature is 60 to 100 ° C.
It is preferable that the treatment is performed for 1 to 24 hours. The processing temperature is 40 ° C
If it is less than, there is almost no effect of reducing the permanent set, which is not preferable, and if it exceeds 120 ° C, there is almost no effect of reducing the permanent set, and if the molded product is deformed or the appearance deteriorates, Yes, it is not preferable. Further, if the treatment time is less than 20 minutes, there is almost no effect of reducing the permanent set, which is not preferable.

The foamed molded product obtained in this way has an expansion ratio of 1.2 to 2.5.
Double, compression set is about 15-40%, and it has dense and uniform closed cells, and it has excellent elasticity for rubber, sealing property, cushioning property, sound insulation property, and heat insulating property. Further, a molded product obtained by extrusion foam molding and obtained by heat treatment has particularly excellent surface smoothness and is particularly suitable for a product field requiring a good appearance.

The compression set referred to in the present invention was measured by the same method as the compression set measurement method of JIS K 6301 using a device (4) having a spacer (3) shown in FIG. 70 ° C x 22
It is a value measured in time.

The measured value of the compression set may vary considerably depending on the shape of the molded product, and the value of 15 to 40% may be, for example, 10 to 45% depending on the shape.

The soft vinyl chloride-based resin composition foam-molded article having a small permanent set thus obtained is, for example, moldings, glass run channels, weather strips, trims,
Various cushioning members, automotive parts such as various sealing members, non-slip, building material parts such as edging of furniture, sealing, etc., sound insulation, vibration isolation, heat insulation, protection, sealing, cushion For the purpose of use, it can be suitably used in a field in which molded articles such as soft vinyl chloride resin, polyurethane and EPDM are used as sheet-shaped, tube-shaped or various shaped articles.

The method for producing a foamed molded product of a soft vinyl chloride resin composition having a reduced permanent set according to the present invention will be described below in more detail with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 10 and Comparative Examples 1 to 3 100 parts of vinyl chloride resin having an average degree of polymerization shown in Table 1 is partially crosslinked N having solubility for MEK shown in Table 1.
BR (acrylonitrile component 33%) in the amount shown in Table 1, methyl methacrylate copolymer having the specific viscosity and glass transition temperature shown in Table 1 in the amount shown in Table 1, dioctyl phthalate (hereinafter referred to as DOP). ) Is the amount shown in Table 1, Ba-
Zn-based stabilizer (3 parts), calcium carbonate (20 parts) and foaming agent were added in the amounts shown in Table 1 and dried up using a super mixer. Obtained powder compound at 140 ℃ 10
After kneading for a minute to prepare a masticated sheet having a thickness of about 3 mm, the masticated sheet was cut into about 3 mm square and pelletized, and extrusion foam molding was performed.

Extrusion foaming molding using L / D = 22, full flight screw of a compression ratio = 3.0, at 50mm single-screw extruder, C ₁ = 155 ° C. from a hopper side cylinder _{temperature, C 2 = 170 ℃, C} 3
= 170 ℃, adapter = 150 ℃, die = 140 ℃,
Carry out at a screw rotation speed of 40 rpm and use a profile extrusion mold (1) having the shape shown in FIG.
Was extruded. The molded product was subjected to free foaming by air cooling and then subjected to heat treatment under the conditions shown in Table 1, subjected to specific gravity measurement and appearance evaluation by the following methods, and then the molded product was subjected to the spacer (3) shown in FIG. Using the device (4) that has
The permanent set was measured by the same method as the method for measuring the compression set of SK 6301. The compression rate was 53%, and the compression condition was 70 ° C. for 22 hours. The results are shown in Table 1.

(Specific gravity and expansion ratio of molded product) The specific gravity was measured by the water substitution method of JIS K 7112, and the specific gravity of the non-foamed molded product was divided by the specific gravity of the foamed molded product to obtain the expansion ratio.

(Appearance of molded product) Visual observation was carried out and surface smoothness and cell condition were evaluated based on the following criteria. In addition, in the cell state, the molded product was cut with a cutter knife and the cut surface was observed.

Surface smoothness ○: Smooth Δ: Concavo-convex is conspicuous ×: Concavo-convex is remarkable Cell state ○: Uniform independent cell △: Cell communication is partially ×: Cell communication is remarkable, and void is present From the results shown in Table 1, when a methyl methacrylate copolymer having a specific viscosity of 1.4 to 2.1 is used, the appearance before heat treatment is poor, but the methyl methacrylate copolymer has a specific viscosity of
It can be seen that the use of 2.9 or more results in a very good appearance of the molded product before heat treatment, and also has a higher expansion ratio than the comparative example. Furthermore, the compression set before heat treatment is as large as 37 to 62% even in the example, but 70 ° C.
By performing heat treatment for 24 hours at 18-40%
It can be seen that it can be lowered to a value equivalent to EPDM.

Examples 11 to 17 and Comparative Examples 4 to 6 The compositions shown in Table 2 were used and evaluated in the same manner as in Example 1. The results are shown in Table 2.

From the results shown in Table 2, the compression set cannot be reduced when the heat treatment temperature is low, and conversely, when it is too high at 130 ° C, not only the compression set cannot be reduced, but also the appearance of the molded product is deteriorated. Recognize. Furthermore, it can be seen that the compression set cannot be reduced if the heat treatment time is as short as 0.2 hours. On the other hand, when the heat treatment time is 0.5 hours or more and the heat treatment temperature is 70 to 100 ° C., it is understood that the compression set can be significantly reduced.

[Advantages of the Invention] The flexible vinyl chloride foam-molded article produced by the method of the present invention is
It has a characteristic that the cells are uniform and have excellent independence, and the permanent set is small, while having a foaming ratio of 2 times or more.

Therefore, it is possible to obtain a soft vinyl chloride-based foam molded article which is excellent in sound insulation, vibration isolation, heat insulation, protection, sealing, cushioning and the like. Furthermore, the extrusion molding method makes it possible to inexpensively and easily produce a molded product having an excellent appearance, and it can be sufficiently used even in the field where only foams of EPDM and polyurethane rubber can be conventionally used. it can.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the tip cross-sectional shape of a die for extrusion molding of a seal member for automobile parts for evaluating compression set of a soft vinyl chloride resin composition foam molded article, and FIG.
It is explanatory drawing which shows the method of measuring a compression set using the test piece manufactured using the metal mold | die shown in FIG.

Claims (2)

[Claims] 1. Containing 5 to 150 parts by weight of acrylonitrile-butadiene rubber dissolved in methyl ethyl ketone in an amount of 5 to 90% by weight, and 0.4 g of a copolymer containing methyl methacrylate as a main component, relative to 100 parts by weight of a vinyl chloride resin. Soft chloride for foaming containing 1 to 60 parts by weight of methyl methacrylate copolymer having a specific viscosity of 2.5 or more in 100 ml of benzene solution measured at 30 ° C, 20 to 200 parts by weight of a plasticizer and 0.5 to 10 parts by weight of a foaming agent. A molded product obtained by foam-molding a vinyl-based resin composition is
A method for producing a soft vinyl chloride foam molded article having a foaming ratio of 1.2 to 2.5 times and a small permanent set, which is characterized by performing a heat treatment at a temperature of to 120 ° C for 20 minutes or more. 2. The method according to claim 1, wherein the heat treatment at a temperature of 40 to 120 ° C. for 20 minutes or more is carried out continuously or intermittently.
The manufacturing method described in the item.