JP3279665B2 - Crosslinked vinyl chloride resin foam and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crosslinked vinyl chloride resin foam and a method for producing the same. More specifically, the present invention relates to a crosslinked vinyl chloride resin foam having a fine cell structure which can be suitably used as a core material for an FRP ship, an FRP tank or the like as a lightweight structural material, and a method for producing the same.

[0002]

2. Description of the Related Art Crosslinked vinyl chloride resin foams are excellent in compressive strength, tensile strength, flexural strength, solvent resistance, etc. and are lightweight, and therefore, for example, unsaturated polyester resins containing a large amount of styrene monomer. It is used as a core material of an FRP laminate using a resin, a core material of various laminated boards, and the like.

However, since the conventional crosslinked vinyl chloride resin foam generally has a large cell diameter, the unsaturated polyester is cast on a core material made of the crosslinked vinyl chloride resin foam at the time of producing an FRP laminate. In this case, a large amount of unsaturated polyester is impregnated in the core material, and when an adhesive is applied on the core material during the production of a laminate, the adhesive is impregnated in the core material in a large amount, and the weight of the final product increases. In addition, there are disadvantages such as an increase in cost.

Conventionally, a so-called specific CFC such as CFC-11 has been generally used as a foaming agent used in producing a foam. There is an urgent need to establish a method for producing a foam without using specific freon.

[0005]

Therefore, in view of the above-mentioned prior art, the present inventors have proposed that even if unsaturated polyester is cast to produce an FRP laminate,
The unsaturated polyester is not impregnated in a large amount, and as a result of repeated studies to produce a foam in which the adhesive is not impregnated in a large amount when the adhesive is applied, in order to produce a laminate,
Density is 0.02-0.5 g / cm ³ , and cell major axis is 0.2-2.2 m
m, a foam having a fine cell structure in which the ratio of the major axis to the minor axis of the cell is 1.0 to 2.0 satisfies the above requirements, and the foam having such a fine cell structure comprises hydrazodicarbonamide as a nucleating agent. And obtained by foaming the foamable composition.

[0006] The present invention has been completed on the basis of such knowledge, but it is also required to use a decomposable foaming agent instead of a specific CFC as a foaming agent used in the foamable composition. In this case, a foam having a fine cell structure was obtained. In this case, it was found that the foam was particularly preferable in terms of protection of the natural environment such as protection of the ozone layer, and the present invention was completed.

[0007]

That is, the present invention provides:
Density 0.02-0.5 g / cm ³ , cell major axis 0.2-2.2m
m, foaming a foamed composition containing a crosslinked vinyl chloride resin foam and a foaming composition containing hydrazodicarbonamide as a nucleating agent, wherein the ratio of the major axis to the minor axis of the cell is 1.0 to 2.0. And a method for producing the crosslinked vinyl chloride resin foam.

[0008]

Action and Examples As described above, the crosslinked vinyl chloride resin foam of the present invention has a density of 0.02 to 0.5 g / cm ³ , a major axis of the cell of 0.2 to 2.2 mm, and a ratio of the major axis to the minor axis of the cell. 1.0
~ 2.0, which is obtained by a method of foaming a foamable composition containing hydrazodicarbonamide as a nucleating agent.

According to the production method of the present invention, the nucleating agent hydrazodicarbonamide is added to the foamable composition, for example, in an amount of 0.1 to 0.1%.
Even when used in a very small amount of 15% by weight,
The cell diameter of the obtained foam is significantly larger than that obtained without adding hydrazodicarbonamide, for example, about 50%.
The above also becomes smaller.

In the production method of the present invention, the foamable composition contains, as a nucleating agent, hydrazodicarbonamide,
A vinyl chloride resin, an isocyanate, an acid anhydride, a foaming agent, and various additives are used as required.

The amount of the hydrazodicarbonamide is 0.01 to 3% by weight based on the foamable composition, especially.
Preferably it is 0.1-0.3% by weight. If the amount is less than the above range, the cell refining effect tends to be insufficient, and if the amount exceeds the above range, the effect does not improve remarkably.

Examples of the vinyl chloride-based resin include copolymers such as vinyl chloride homopolymer and vinyl chloride-vinyl acetate copolymer, and blend resins exhibiting compatibility with vinyl chloride, such as chlorinated vinyl chloride. The concept includes a mixture with at least one kind of resin, chlorinated polyethylene, ethylene-vinyl acetate copolymer and the like. Incidentally, the polymerization degree of the vinyl chloride resin is usually 1000 to 4000,
Preferably, it is 1500-3000. In the present invention, among the vinyl chloride resins, the paste vinyl chloride resin can be a so-called sol-like foamable composition having fluidity, provided that it is industrially convenient to handle. Therefore, it can be suitably used. Here, the paste vinyl chloride resin is a pearl-like fine powder having a particle diameter of several μm or less, and is produced by a so-called emulsion polymerization method or microsuspension polymerization method,
The fine powder is composed of many fine particles having a smaller diameter.

The amount of the vinyl chloride resin is usually 20 to 90% by weight, preferably 30 to 60% by weight, based on the foamable composition. When the amount of the vinyl chloride resin is less than the above range, the cell membrane of the foam may be broken at the time of foaming and may not be a good foam, and when the amount is more than the above range, However, the density of the foam increases, and the value as a lightweight structural material tends to be lost.

Further, since the foam to be used in the present invention is a crosslinked foam, an isocyanate and an acid anhydride are blended in the foamable composition.

Examples of the isocyanate include toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). These isocyanates are usually used alone or in combination of two or more.

The compounding amount of the isocyanate is usually 20 to 50% by weight, preferably 30 to 40% by weight, based on the foamable composition. If the amount is less than the above range, the crosslinking effect tends to decrease,
If the amount is larger than the above range, the crosslinking reaction tends to take a long time. The isocyanate reacts when an acid anhydride and water coexist, and carbon dioxide gas is generated at the same time as crosslinking proceeds. Therefore, the carbon dioxide gas can be used as a foaming agent. When the carbon dioxide gas thus generated is used as a blowing agent, the amount of the isocyanate is preferably 20% by weight or more, more preferably 25% by weight or more based on the foamable composition.

Examples of the acid anhydride include phthalic anhydride and maleic anhydride. These acid anhydrides are used alone or in combination of two or more. Since the acid anhydride does not directly react with the isocyanate, the foamable composition is foamed to form a primary foam, and the obtained primary foam is contacted with hot water or steam to remove the acid anhydride. It is preferred that a dicarboxylic acid is reacted with the isocyanate to cause secondary foaming and, at the same time, advance a crosslinking reaction.

The amount of the acid anhydride is usually 0.5 to 1.5 equivalents, particularly preferably 1 equivalent, of carboxyl groups formed when the acid anhydride is reacted with water per 1 equivalent of the isocyanate group of the isocyanate. It is desirable to adjust to. When the amount exceeds the above range and when the amount is less than the above range, unreacted substances remain, and there is a tendency that various physical properties of the obtained foam are reduced.

The isocyanate and the dicarboxylic acid react with each other to form a cross-link, thereby forming a three-dimensional network structure. The three-dimensional network structure is entangled with the vinyl chloride resin in the order of molecular size, and a part of the three-dimensional network is grafted with the vinyl chloride resin, whereby the hardness of the foam is improved and the mechanical strength is improved.

A foaming agent is blended with the foamable composition. Such a foaming agent is roughly classified into a decomposable foaming agent and an evaporative foaming agent, and any of the foaming agents may be used in the present invention. preferable.

Examples of the decomposition type foaming agent include azobisisobutyronitrile, azodicarbonamide, diazoaminobenzene, N, N'-dinitrosopentamethylenetetramine, p-toluenesulfonylhydrazide and the like. The blowing agents may be used alone or in combination of two or more.

Examples of the evaporating foaming agents include propane, butane, and soft freon such as Freon-123. These foaming agents may be used alone or in combination of two or more. Note that among these, it is preferable to use propane, butane, or the like, which has a small effect on the ozone layer.

The amount of the foaming agent varies depending on the amount of the isocyanate and the acid anhydride, the desired expansion ratio, the type of the foaming agent, and the like, and cannot be unconditionally determined. 0.1 to 10% by weight, preferably 0.3 to 7% by weight, more preferably 0.5 to 5% by weight. If the amount of the foaming agent exceeds the above range,
The foamable composition leaks from the mold during multi-stage pressing,
At the time of foaming, there is a tendency that the cell membrane is easily broken, and when it is less than the above range, a desired foaming ratio tends to be not obtained.

The foaming agent may be used, if necessary, in combination with, for example, a urea-based foaming aid.

If necessary, the foaming composition may contain, for example, a stabilizer, an inorganic filler (extender), a pigment, a nucleating agent other than hydrazodicarbonamide in an appropriate amount.

The stabilizer is not particularly limited as long as it has an ability to prevent decomposition and deterioration of the vinyl chloride resin. Specific examples of such stabilizers include, for example, dibasic lead stearate, dibasic lead phosphite, tribasic lead sulfate and zinc stearate, calcium stearate,
Examples thereof include lead phosphite, and these stabilizers are used alone or in combination of two or more.

The inorganic filler includes a fibrous material and a granular material. Representative examples of the fibrous material include rock wool, glass fiber, and ceramic fiber. Representative examples of the granular material include, for example, talc, calcium carbonate, shirasu balloon and the like.

The pigment is for coloring the obtained foam into a desired color. In addition to a white pigment which can also serve as an inorganic filler, such as calcium carbonate, etc., for example, titanium white , Benzidine orange, benzidine yellow, watching red and the like.

Examples of the other nucleating agents include talc, baking soda, citric acid, ultramarine, ethylenebisstearylamide and the like, and these can be used alone or as a mixture of two or more.

In the present invention, for example, tertiary amines such as various antioxidants and ultraviolet absorbers,
What is usually used as an additive for plastics, such as an antistatic agent such as an alkyl sulfonate, can be appropriately added to the foamable composition.

In the production method of the present invention, the foamable composition is sufficiently kneaded with a kneading machine such as a double-arm kneader before filling it into a mold, to obtain a sol having a uniform composition. Preferably. The temperature at the time of kneading is not particularly limited, and may be room temperature.

Next, the foamable composition thus prepared is filled in a mold made of, for example, an aluminum alloy or the like, and the mold is set in, for example, a hydraulically driven multi-stage hot press or the like. Heat the composition.

The conditions for pressurization and heating vary depending on the constituents of the foamable composition, but appropriate temperatures according to the foamable composition, for example, 150 to 200 ° C., and pressures of 100 to 300 kg / kg.
cm ² · G is selected. When the temperature reaches the above range, it is preferable to maintain that state for about 30 to 60 minutes.
Thereafter, the temperature of the pressurized heating plate of the press machine is lowered to room temperature using a cooling medium such as water while the mold is kept pressed, and the mold is opened to obtain a primary foam. .

The acid anhydride in the foamable composition does not directly react with the isocyanate, but the acid anhydride becomes a dicarboxylic acid in the presence of moisture, and the resulting dicarboxylic acid reacts with the isocyanate. Therefore, the obtained primary foam is brought into contact with water vapor or hot water to advance the crosslinking reaction, and at the same time, secondary foaming is performed by the generated carbon dioxide gas. In this case, the temperature of steam or hot water is about 80 to 130 ° C., preferably 85 to 110 ° C., and more preferably 90 to 100 ° C., in order for the crosslinking reaction and secondary foaming to proceed sufficiently.
° C. If the temperature is lower than 80 ° C., the foam does not foam to a predetermined size, or even if foaming takes a long time for secondary foaming, and if it exceeds 130 ° C., the cell membrane is broken. Tend. The temperature is desirably 100 ° C. or lower in order to prevent equipment costs from increasing due to the need for heating equipment.

The foam thus obtained has been crosslinked by the reaction of an isocyanate and a dicarboxylic acid,
Density is 0.02-0.5 g / cm ³ , and cell major axis is 0.2-2.2 m
m, since the value of the ratio of the major axis to the minor axis of the cell is 1.0 to 2.0, it is not only high in hardness and excellent in various mechanical properties, but also finer cell structure compared to the conventional foam. Therefore, it can be suitably used as a core material of an FRP ship or the like that requires light weight.

The density of the foam of the present invention is 0.02 g /
If it is less than ³ cm, the mechanical strength will decrease,
When the amount exceeds 0.5 g / cm ³ , the heat insulating property is reduced, the weight is not sufficient, and the cost is increased. Therefore, 0.02 to 0.5 g / cm ³ , preferably 0.03 to 0.3 g / cm ³ .
It is assumed to be ³ .

Here, the major axis of the cell refers to the length of the cell in the thickness direction of the foam. When the major axis of the cell is smaller than 0.2 mm, the cell having substantially the same diameter as the cell has the major axis. When it is difficult to form a body, and when the thickness exceeds 2.2 mm, the amount of impregnation when an adhesive or the like is applied increases, so that the thickness is 0.2 to 2.2 mm, preferably 0.5 to 2.0 mm.

The minor axis of the cell refers to the length of the cell in the width / length direction of the foam. The ratio of the major axis to the minor axis of the cell (major axis of the cell / minor axis of the cell) If it is smaller than 1.0, the compressive strength is small, and if it is more than 2.0, the heat insulating property is reduced, so that it is 1.0 to 2.0, preferably 1.3 to 1.6.

Next, the crosslinked vinyl chloride resin foam of the present invention and the method for producing the same will be described in detail with reference to Examples, but the present invention is not limited to only these Examples.

Examples 1 to 7 Raw materials were adjusted to have the composition shown in Table 1, and the total amount was 50 kg.
Then, the mixture was kneaded with a double-arm kneader having an effective volume of 50 liters at room temperature for 45 minutes to obtain a foamable composition.

The obtained foamable composition was 680 mm × 33 in inner size.
Each of the molds was filled into ten 5 mm × 14 mm aluminum alloy molds and set in a multi-stage press. Pass the steam through the press hot plate, raise the mold temperature to 175 ℃, pressure 210 kg
/ Cm ² · G for 35 minutes, then cool it down to below 30 ° C by passing industrial water through a hot plate, release the clamping pressure of the press, open the mold and release the primary foam. I got it. The expansion ratio of the obtained primary foam was 1.2 to 1.5 times.

Next, the obtained primary foam was left in hot water having a temperature shown in the secondary foaming conditions shown in Table 1 for a predetermined time to carry out a crosslinking reaction, and at the same time foaming by the generated carbon dioxide gas was further performed. And a secondary foam was obtained.

The obtained secondary foam was put into industrial water at about 30 ° C., left standing for 30 minutes, cooled, taken out and air-dried, and the expansion ratio of the secondary foam was measured.
~ 44 times.

Next, the secondary foam was finished to a size of 1820 mm × 910 mm × 50 mm using a finishing work planner and a circular saw, and the density, cell diameter and surface hardness of the secondary foam were examined according to the following methods. . The results are also shown in Table 1.

(A) Density The density is determined by measuring the weight (g) and volume (cm ³ ) of the secondary foam.

(B) Cell Diameter The major axis and minor axis of 7 to 15 cells are measured using a graduated loupe (× 10), and the average value is determined.

(C) Surface Hardness A test piece having a size of 100 mm × 100 mm × 10 mm was cut out from the secondary foam, and an unsaturated polyester solution containing 45% by weight of a styrene monomer was applied to one surface of the test piece. After leaving for a while, the surface hardness of the other one side (non-coated side) is measured using Asker Rubber Tester Type CS manufactured by Kobunshi Keiki Co., Ltd.

The surface hardness is a measure of the degree of softening of the foam by the styrene monomer, and is a measure of the degree of crosslinking of the foam.

Comparative Examples 1-2 Examples 1-2 were obtained except that hydrazodicarbonamide was not used as a nucleating agent and the blowing agent was changed as shown in Table 2.
A foam was obtained in the same manner as described above.

The density, cell diameter and surface hardness of the obtained foam were examined in the same manner as in Examples 1 to 7. Table 2 shows the results.

Each abbreviation in the table means the following.

PSH-650A: paste resin (manufactured by Kaneka Chemical Co., Ltd., average degree of polymerization: 2400) HDA: hydrazodicarbonamide TDI: toluene diisocyanate PA: phthalic anhydride SL: dibasic lead stearate CC: Calcium carbonate BY: Benzidine yellow BO: Benzidine orange WR: Watching red AIBN: Azobisisobutyronitrile ACA: Azodicarbonamide

[0053]

[Table 1]

[0054]

[Table 2]

From the results shown in Tables 1-2, Examples 1-7
It can be seen that the foam obtained has a cell diameter as small as about 50% in comparison with the foams obtained in Comparative Examples 1 and 2, though the density of the foam hardly changes.

[0056]

According to the production method of the present invention, the density is from 0.02 to
A crosslinked vinyl chloride resin foam having 0.5 g / cm ³ , a cell major axis of 0.2 to 2.2 mm, and a ratio of cell major axis to minor axis of 1.0 to 2.0 can be easily produced without using a specific Freon. The obtained foam can be used in FR where weight reduction is required.
It can be suitably used as a core material for P ships, FRP tanks and the like.

Claims (5)

(57) [Claims] 1. A cell having a density of 0.02 to 0.5 g / cm ³ , a major axis of a cell of 0.2 to 2.2 mm, and a ratio of a major axis to a minor axis of a cell of 1.0 to 2.
0. A crosslinked vinyl chloride-based resin foam characterized by being 0. 2. The process for producing a crosslinked vinyl chloride resin foam according to claim 1, wherein a foamable composition containing hydrazodicarbonamide as a nucleating agent is foamed. 3. A primary foam obtained by foaming a foamable composition containing a vinyl chloride resin, a nucleating agent hydrazodicarbonamide, an isocyanate, an acid anhydride and a foaming agent is heated at 80 to 130 ° C. 3. The method for producing a crosslinked vinyl chloride resin foam according to claim 2, wherein the foam is secondary foamed while the vinyl chloride resin is crosslinked by contact with water or steam. 4. The method for producing a crosslinked vinyl chloride resin foam according to claim 3, wherein the foaming agent is a decomposable foaming agent. 5. The compounding amount of the foaming agent is based on the foamable composition.
5. The method for producing a crosslinked vinyl chloride resin foam according to claim 3, wherein the content is 0.1 to 10% by weight.