JPS6329718B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Objects of the Invention) The first object of the present invention is primarily to bond groups of chips of soft plastic foam and to change the physical properties of the foam.

A second object of the present invention is to provide a simple and quick reaction when molding chips.

Another object of the present invention is to improve productivity and reduce costs.

(Prior art) In the past, chips were made by crushing various pieces of soft plastic foam, which were then sprayed with adhesive and subjected to a compression reaction in a mold to obtain a desired molded product. In the past, the function of adhesive was limited to simply bonding chips together.

Therefore, the influence of the adhesive on the product is singular, and furthermore, the degree of influence on the product has not been considered in advance. As a result, the properties of molded products obtained from chips are inherently limited, and it has been extremely difficult to provide them with a wide range of physical properties.

(Structure of the Invention) The present invention is an adhesive that eliminates the above-mentioned drawbacks and provides a wide range of properties for chip products. The density of the product is one of the factors that greatly influences the physical properties of the chip foam, and the present invention aims to easily increase the physical properties of the chip product by using an adhesive without changing the weight of the product. . The chip adhesive for this purpose is generally made by mixing polymethylene polyphenyl isocyanate (hereinafter referred to as ``MDI'') with a urethane prepolymer obtained by reacting tolylene diisocyanate (hereinafter referred to as ``TDI'') and polyol. The adhesive for chips is prepared by adding a solvent to this mixture, if necessary.

When looking at the physical properties of chip foam products, the main ones include hardness, strength, elongation, impact resilience, and shock absorption. The aim is to make it possible to change these physical properties with just a single touch, and to make chip foam products all-round.

Therefore, the present inventors focused on "MDI" to obtain the hardness and impact absorption properties of the chip molded product, and on the other hand, focused on urethane prepolymers to obtain the elongation and impact resilience. Depending on the physical properties of the final product, we use adhesives with excess MDI for products that require hardness and shock absorption, and use adhesives that contain excess urethane prepolymer for products that require elongation and impact resilience. It's about doing.

The basic composition of the present invention is made by mixing an appropriate amount of urethane prepolymer with "MDI",
One component of this, MDI, reacts with water to form urea bonds, and urea bonds generally have a strong crosslinking distribution of hydrogen bonds, giving them excellent physical properties as a hard segment. This "MDI"
belongs to the category of isocyanate compounds, and has the advantage of being less expensive and more reactive than other isocyanates.

Additionally, since MDI generally has a low clay content compared to other thermosetting resins, it has the advantage of being more effective in terms of workability, and it also has the great advantage of reacting easily and quickly with moisture. It is something.

The other material of the adhesive of the present invention, the urethane prepolymer, has a low percentage of terminal NCO groups and is made by reacting "TDI" with a polyol.

The properties of urethane prepolymers are greatly influenced by the isocyanate and polyol that are the raw materials for their composition, but if the isocyanate is limited to "TDI" as in the present invention, the properties are greatly influenced by the polyol. It turns out.

That is, it is influenced by the molecular weight and number of functional groups of the polyol. Specifically, in order for the urethane prepolymer to have a rubber-like elastic property after being cured by moisture, a polyol with a functional group number of 2 to 4 and a molecular weight of about 1500 to 4000 is usually used.
On the other hand, it is necessary to suppress the percentage of free NCO groups in the urethane prepolymer to about 15% or less.

The reason for selecting polyol is that when producing a prepolymer, isocyanate reacts with polyol to form urethane bonds, and the degree of branching and molecular weight of these bonds are adjusted so that these bonds exhibit high elastic properties.

Furthermore, it is a reactive group of the urethane prepolymer.
The reason for keeping the NCO group low is to increase the number of urethane bonds that give high elastic properties, and to make the prepolymer highly elastic after curing.

Therefore, the adhesive of the present invention is prepared by preparing a urethane polymer that becomes a rubber-like elastic body after curing, and on the other hand, adding "MDI" that gives hardness to the prepolymer in accordance with the physical properties of the final product to be obtained. It can be easily obtained by simply mixing an appropriate amount.

Incidentally, "MDI" and the urethane prepolymer are easily mixed together and do not produce any other reaction products.

Furthermore, it is preferable to mix a solvent with the adhesive so that the adhesive can be easily and uniformly applied to the chip material.

Solvents include benzene, toluene, xylene,
Aromatic hydrocarbon solvents such as chlorobenzene, aliphatic hydrocarbon solvents such as n-hexane, chlorinated solvents such as methylene chloride, 1,1,1-trichloroethane, propane dichloride, ethyl acetate, latyl acetate, etc. Examples include ester solvents and ketone solvents such as acetone and methyl ethyl ketone.

These may be used alone or in combination. Although there is no particular restriction on the amount of adhesive to be mixed, it is desirable to mix the adhesive so that the clay content is 500 cp or less during production.

An example of the use of the present invention is to create a molded product by hot press, in which a liquid is prepared by mixing the above-mentioned urethane prepolymer with "MDI" in a proportion according to the desired physical properties after curing, and a solvent such as methylene chloride is required. Add an appropriate amount depending on the amount, spray it mainly onto chips such as soft plastic foam, and use a rotary mixer or the like to penetrate into the cells of the evenly formed chips.

Next, it is placed in a hot press mold, compressed, and heated with steam, which causes an immediate reaction and completes the molding.

In addition, when the NCO group, which is a reactive group in an adhesive, imparts high elastic properties, it is low, and when it imparts properties such as hardness, it increases, but in general, the fewer reactive groups there are, the faster the reaction completes, but the more Since "MDI" added to give this property is an extremely reactive isocyanate compound, this adhesive is highly reactive in both cases.

That is, when imparting properties such as high elasticity, the percentage of NCO groups is low, and when imparting properties such as hardness, the NCO groups in the adhesive increase due to "MDI".

The composition ratio ψ (MDI weight ratio/urethane prepolymer weight ratio) of the mixing amount of "MDI" to the urethane prepolymer in the adhesive of the present invention is set, and the hardness, hand strength, elongation rate, and Changes in rebound resilience and impact acceleration are shown in FIGS. 1 to 5, respectively.

In addition, as a sample, the material is a crushed product of soft urethane foam, and the adhesive is applied to 1 kg of this crushed product.
This is a specimen made from a urethane chip form block with a specific gravity of 0.1 that was coated with 250 g and molded.

Figure 1 shows the change in hardness depending on the ratio of the amount of "MDI" mixed to the urethane prepolymer of the adhesive.

In other words, the left end of the horizontal area is urethane prepolymer.
100%, and the right end is MDI 100%. That is, ψ
This means that as the value approaches 1, the MDI amount increases. The vertical axis shows the scale of hardness under 25% compression. The figure shows that the more MDI is mixed, the harder the material becomes.

FIG. 2 also shows the change in the tensile strength of the urethane chip foam due to the difference in the mixing ratio of the urethane prepolymer and MDI in the adhesive.

FIG. 3 also shows the change in the elongation rate of the urethane chip foam due to the difference in the mixing ratio of the urethane prepolymer and MDI as adhesives. As is clear from the figure, the elongation rate increases as the amount of urethane prepolymer mixed in the adhesive increases.

FIG. 4 also shows the change in the impact resilience of the urethane chip foam due to the difference in the mixing ratio of the urethane prepolymer and MDI in the adhesive. . Similarly to FIG. 3, it can be seen that the greater the amount of urethane prepolymer mixed in the adhesive, the greater the impact resilience.

FIG. 5 also shows the change in impact acceleration of the urethane chip foam due to the difference in the mixing ratio of the urethane prepolymer and MDI as adhesives. As is clear from the figure, in the adhesive
It can be seen that the greater the amount of MDI mixed, the greater the impact acceleration.

Chip molded products with various physical properties can be obtained by easily changing the mixing amounts of "MDI" and urethane prepolymer, which are constituent materials of the adhesive, to create products that meet the required physical properties. In other words, this adhesive has made it possible to create a wide range of products that meet various needs using chip molded products.

Although the adhesive according to the present invention has been described in terms of pulverized chips made of soft plastic foam, the adhesive can also be used in other applications such as pulverized felt, fabric, non-woven fabric, and chips made of the above-mentioned soft plastic foam. A sufficient effect can be expected even in a mixture of the following.

[Brief explanation of the drawing]

Figure 1 is a graph showing changes in the hardness of the urethane chip foam as the composition ratio ψ of the MDI and urethane prepolymer mixture changes, and Figure 2 is the composition ratio of the MDI and urethane prepolymer mixture. A graph showing the change in tensile strength of urethane chip foam as ψ changes, Figure 3 is "MDI"
A graph showing the change in the elongation rate of the urethane chip foam as the composition ratio ψ of the urethane prepolymer mixture and MDI changes. FIG. 5 is a graph showing the change in impact resilience of the urethane chip foam. FIG. 5 is a graph showing the change in the impact acceleration of the urethane chip foam as the composition ratio ψ of the MDI and urethane prepolymer mixture changes.

Claims (1)

[Claims] 1. Polymethylene polyphenyl isocyanate
An adhesive for chip molding, mainly for soft plastic foam, which is made by mixing a urethane prepolymer made by reacting tolylene diisocyanate and a polyol so as to keep the NCO group percentage within 15%. 2. An adhesive for chip molding mainly for soft plastic foam, which is further mixed with a solvent, as claimed in claim 1.