JPS588346B2 - Method for manufacturing resin-impregnated sheet overlay concrete formwork plywood - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a highly durable resin-impregnated sheet overlay concrete form plywood.

Plywood has traditionally been widely used for concrete formwork because it is light, strong, inexpensive, and manufactured in large quantities.

However, concrete formwork made of plywood can be used less frequently than formwork made of steel, and the finished concrete surface is imprinted with pipe grooves on the plywood surface, resulting in an uneven finish.

Depending on the resin of the veneer that makes up the plywood, there are drawbacks such as inhibiting the hardening of cement.

Recently, in order to solve the above drawbacks, plywood surfaces have been coated with alkali-resistant synthetic resin paint, synthetic paper made from synthetic resins such as polyethylene resin or polystyrene resin has been pasted, and plywood has been made using phenolic resin or melamine resin. Papers impregnated with condensation polymerization type synthetic resins such as Diaryl Phthalate resin and addition polymerization type synthetic resins such as diallyl phthalate resin are commercially available.

However, although the commercially available concrete form plywood has improved the above-mentioned drawbacks, it still has the following drawbacks.

In other words, plywood surfaces coated with alkali-resistant synthetic resin paint or synthetic paper pasted have lower surface hardness than those made from hot-press molded impregnated paper, and can be reused only a few times because of their lower surface hardness.

Impregnated paper molded under heat and pressure has high surface hardness and durability, but condensation polymerization type resins such as phenolic resin and melamine resin tend to cause cracks along the pipe grooves of the plywood. Once cracks occur, the releasability from the concrete surface becomes extremely poor.

In addition, in the case of phenolic resin, the alkaline component of the cement stains the concrete surface in a reddish-brown color, significantly impairing its aesthetic appearance.

Addition polymerization type resins such as diallyl phthalate resins do not contaminate the concrete surface and can be reused once.
The number of times is often 0 or more, but impregnated paper tends to peel between sheets and is very expensive.

The present invention has been made to solve the above-mentioned drawbacks of concrete formwork and to significantly increase the number of times it can be used.

That is, in the present invention, after impregnating a base material such as paper or cloth with a resin liquid containing an amino resin soluble in water or lower alcohol, an appropriate amount of a curing agent, an additive, and polyethylene oxide having a molecular weight of 1000 or more, After drying to form an impregnated sheet, the impregnated sheet is stacked on the surface of a substrate such as plywood and bonded by hot pressure molding to produce concrete form plywood.

To explain the present invention in detail, the water- or lower alcohol-soluble amine resin used in the present invention refers to thermosetting synthetic resins such as urea resin, melamine resin, acetoguanamine resin, and benzoguanamine resin.

These resins have excellent adhesion to wood, good chemical resistance and stain resistance, and are hard and resistant to wear.

The reason why the resin is limited to one that is soluble in water or lower alcohol is that the polyethylene oxide added to the resin liquid is hydrophilic and insoluble in aliphatic hydrocarbons.

Next, blending polyethylene oxide with a molecular weight of 1000 or more into the above amino resin plasticizes the amine resin, stabilizes the dimensions of the wood fibers on the plywood surface, and prevents the occurrence of cracks in the resin-impregnated sheet layer. In addition to suppressing
Polyethylene oxide precipitates on the surface of the resin-impregnated sheet layer to form a thin film, which has the effect of improving mold releasability from the concrete surface, and these synergistic effects significantly increase the number of times it can be used as concrete formwork. be.

Traditionally, polyethylene oxide is hydrophilic and generally has excellent properties such as chemical resistance, heat resistance, and flexibility, so it has been used as a surfactant, pharmaceuticals, cosmetics, and a plasticizer for synthetic resins. It is also known to improve dimensional stability.

For example, as a plasticizer for synthetic resins, the molecular weight is 200 to 60.
Generally, a liquid of about 0 is used.

When the molecular weight exceeds 1000, it changes from a semi-solid to a waxy solid, so it is often used as a molding lubricant or mold release agent in the rubber industry.

Therefore, in the present invention, we focused on the properties of these polyethylene oxides, and as a result of experiments, we found that by using resin-impregnated paper made by blending polyethylene oxide with a molecular weight of 1000 or more with amine resin soluble in water or lower alcohol, we can create concrete with excellent durability. Formwork plywood was obtained.

In other words, when a resin-impregnated sheet made by blending polyethylene oxide with a molecular weight of 1000 or more into a synthetic resin is hot-press molded onto the surface of plywood, the synthetic resin itself is first plasticized by the polyethylene oxide, and cracking of the impregnated sheet due to condensation of the synthetic resin itself can be suppressed. .

In addition, the polyethylene oxide contained in the resin that has penetrated into the plywood surface as an adhesive penetrates into the wood fibers and suppresses expansion and contraction due to moisture changes on the plywood surface, thereby suppressing cracks in the resin-impregnated sheet caused by expansion and contraction of the base material. be done.

Furthermore, since polyethylene oxide has a large molecular weight, a portion of it precipitates on the surface of the resin-impregnated sheet that has been molded under heat and pressure, forming a thin wax-like film, which improves the mold release ability from the concrete surface.

Due to the synergistic effect of the above effects, the concrete formwork plywood of the present invention has a resin-impregnated sheet layer that is less prone to cracking and can be used 20 to 30 times, which is 1.5 to 2 times more than conventional plywood. .

As the curing agent, a latent curing agent such as an ammonium salt or an ammonium sulfonate salt, or an inorganic or organic acid such as hydrochloric acid or paratoluenesulfonic acid is used.

Examples of additives include penetrating agents such as various surfactants and internal mold release agents such as higher fatty acids.

Next, examples of the present invention will be described.

Example 1 100 parts by weight of a melamine resin solution dissolved in methanol so that the resin solid content was 40% was added with a molecular weight of 2000 to 3000.
5 parts by weight of polyethylene oxide, 1 part by weight of internal mold release agent, and 0.5 parts of ammonium sulfonate as a hardening agent.
Kraft paper weighing 100 g/m2 was immersed in the mixed resin solution in parts by weight, and then dried at 100 to 110 DEG C. for 2 minutes to obtain impregnated paper with an impregnation rate of 57%.

Next, this impregnated paper was layered on a plywood surface with a thickness of 12 mm, and then heated in a hot press at a temperature of 120 to 130°C and a pressure of 13 mm.
A melamine resin-impregnated paper overlay concrete form plywood was obtained by hot-pressing molding under the conditions of kg/cm2 and 10 minutes.

The form plywood was repeatedly used for concrete molding 20 times in a row, but no cracks were generated on the surface, and the mold releasability was good with almost no deterioration.

Example 2 100 parts by weight of a urea resin solution dissolved in water so that the resin solid content was 42%, 10 parts by weight of polyethylene oxide with a molecular weight of 5,000 to 7,000, 0.5 parts by weight of an internal mold release agent, and ammonium chloride as a hardening agent. After immersing a piece of kraft paper weighing 200 g/m2 in a resin solution mixed with 0.4 parts by weight, 1
The paper was dried at 00 to 110°C for 4 minutes to obtain impregnated paper with an impregnation rate of 55%.

Next, this impregnated paper was layered on a plywood surface with a thickness of 15 mm, and then heated in a hot press at a temperature of 110 to 120°C and a pressure of 15 mm.
kg/cm2 for 15 minutes to obtain a urea resin-impregnated paper overlay concrete form plywood.

It was used as a concrete formwork in the same manner as in Example 1, and the results were good.

Example 3 A benzoguanamine-urea cocondensation resin solution with a molecular weight of 1000 to 3000 was dissolved in water so that the resin solid content was 50%.
7 parts by weight of polyethylene oxide, 0.5 parts of internal mold release agent
Part by weight and 0.0% ammonium sulfonate salt as curing agent.
After immersing a nonwoven fabric made of cellulose fibers weighing 150 g/m2 in a resin solution mixed with 5 parts by weight,
It was dried at 0° C. for 7 minutes to obtain an impregnated sheet with an impregnation rate of 60%.

Next, this impregnated sheet was layered on a plywood surface with a thickness of 15 mm, and then heated at a temperature of 120 to 130 °C and a pressure of 1 in a hot press.
A resin-impregnated paper overlay concrete form plywood was obtained by hot-pressing molding at 8 kg/cm2 for 20 minutes.

The formwork was used repeatedly for concrete molding 30 times in a row, but no cracking or peeling occurred on the surface, and almost no deterioration in mold release performance was observed.

Note that the impregnation rate in the present invention refers to the following.

Claims (1)

[Claims] 1. After impregnating a base material such as paper or cloth with a resin liquid prepared by blending an amine resin soluble in water or lower alcohol with an appropriate amount of a curing agent, additives, and polyethylene oxide with a molecular weight of 1000 or more. A method for manufacturing a resin-impregnated sheet overlay concrete formwork plywood, in which the impregnated sheet is appropriately dried to form an impregnated sheet, and then the impregnated sheet is overlaid on the surface of a substrate such as plywood and bonded by hot pressure molding. 2. The method for manufacturing a resin-impregnated sheet overlay concrete form plywood according to claim 1, wherein the amine resin soluble in water or lower alcohol is a melamine resin.