JPH03157433A - Electrically conductive polyurethane foam - Google Patents

Abstract

PURPOSE:To obtain an electrically conductive urethane foam improved in fixing properties and dispersion of an electrically conductive material by dispersing a water-dispersible binder and a nonionic surfactant having a low HLB in a dispersion of fine electrically conductive powder and fine mica powder and impregnating a urethane foam therewith. CONSTITUTION:The objective urethane foam obtained by dispersing (B) a water- dispersible binder, (C) a nonionic surfactant having 8-11 HLB and preferably (D) a rust preventive agent in (A) a dispersion prepared by dispersing fine electrically conductive powder and fine mica powder expressed by the formula [A is K, Na or Ca; B and C are Fe(II), Fe(III), Mn, Al, Mg or V; D is Si or Al] in water using a nonionic surfactant having >=12 HLB, preparing an electrically conductive treating liquid and fixing the resultant liquid to a urethane foam. Thereby, balance between controllability and hardly falling off properties of IC lead frames is suitably regulated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a post-treated conductive urethane foam used for wrapping, packaging and transporting parts related to electronic equipment, particularly TC.

(Prior art) Conventionally, the composition of conductive foams has been to mix and add conductive substances such as carbon black to foams such as polyethylene, polyurethane, and synthetic rubber. There are two methods: a method of blending and simultaneous foaming, and a method of post-processing the conductive material mixture into a foam.

Although the former method has the advantage that a conductive foam can be obtained in the second step, the amount of conductive material added is limited due to the foaming characteristics, and the conductivity is also limited. Also,
This simultaneous foaming method has problems such as poor adhesion of the conductive substance to the foam (and large variations in conductivity).

On the other hand, the latter is generally manufactured by impregnating the foam with an aqueous dispersion-based conductive treatment liquid that does not cause problems such as swelling or deterioration of the foam, and then drying it. Although the method using a liquid requires impregnation and drying steps, it is a very useful method because the resistance value can be controlled over a wide range by changing the formulation of the treatment liquid and the amount of coating.

However, in this method, it is not enough to simply disperse a conductive substance such as carbon black, graphite, or conductive whiskers in water using a dispersant and prepare a conductive treatment liquid with a water-dispersible binder such as an emulsion. In particular, as the thickness of the foam increases, it is quite difficult to impregnate the foam uniformly, resulting in large variations in conductivity.
Performance is often unsatisfactory. Furthermore, for example, when the conductive urethane foam produced in this way is used for packaging, packaging, or transportation to prevent IC destruction, the IC lead frame is inserted into the conductive urethane foam. However, it is difficult to adjust the balance between ease of stabbing and difficulty in coming off by simply selecting the material and adjusting the amount of adhesion.

[Problem to be solved by the invention]

The present invention was made against the background of the above-mentioned problems of the prior art, and improves the adhesion of the conductive material to the urethane foam and the variation in conductivity, and adjusts the balance between ease of insertion and difficulty in pulling out the IC lead frame. The purpose of the present invention is to provide a conductive urethane foam.

[Means for Solving the Problems] The present invention uses a nonionic surfactant with an HLB of 12 or more to produce conductive fine powder and the following formula (1) % formula %) (1) [wherein A is K, Na or Ca, B or C is F
e (II), Fe (I[l), Mn, Aj
2. Dispersion K in which fine mica powder represented by Mg or ■, D represents Si or A2 is dispersed in water, a water-dispersible binder, and a nonionic surfactant with an HLB of 8 to 11 are dispersed. A conductive urethane foam is provided by preparing a conductive treatment liquid and impregnating and fixing the same into the urethane foam.

The present invention uses a nonionic surfactant with an HLB of 12 or more, thereby uniformly dispersing the conductive fine powder and the mica fine powder in the conductive treatment liquid, and K, HL.
By rapidly penetrating the inside of the urethane foam with a nonionic surfactant having B of 8 to 11 and fixing it by drying the water-dispersible binder, and further by incorporating a rust preventive agent into the conductive treatment liquid. This is an attempt to solve the above problem.

In the present invention, a nonionic surfactant having an HLB of 12 or more is used as a dispersant for dispersing conductive fine powder and mica fine powder in water.

Ionic surfactants have an HLB of 12 because they tend to form bubbles and have an affinity for water, which is a dispersion medium.
The above nonionic surfactants are used as dispersants. Even when a nonionic surfactant with an HLB of less than 12 is used as a dispersant, the conductive fine powder and the mica fine powder are not uniformly dispersed in the dispersion liquid.

Examples of the nonionic surfactant include polyethylene glycol alkyl phenyl ether alkyl ether having an HLB value of 12 or more. Two or more types of nonionic surfactants having an HLB value of 12 or more can also be used in combination.

The amount of the nonionic surfactant with an HLB of 12 or more used as a dispersant is not particularly limited, but is preferably the minimum necessary amount, and is preferably 1 to 20 parts by weight based on 100 parts by weight of the total amount of fine powder used. use.

Specially, when using highly conductive carbon black as the conductive fine powder, it is necessary to use a larger amount, but when using conductive potassium titanate whiskers, it is sufficient to use a small amount.

As the electrically conductive fine powder of the present invention, carbon black or graphite is useful in terms of electrical conductivity and economy. Examples of carbon black include ordinary furnace black, thermal black, channel black, acetylene black, color You can use any color including black.

In addition, for the white-gray color, conductive potassium titanate whiskers (antimony-doped tin oxide coated product), conductive zinc oxide, conductive zinc oxide whiskers, etc. are useful because they can relatively freely color the conductive processing liquid. Of these, conductive potassium titanate whiskers are particularly useful because they can provide the necessary conductivity with a relatively small amount.

These conductive fine powders preferably have an average particle size of 0.01 to 100 μm from the viewpoint of dispersion workability.

The amount of conductive fine powder used is preferably more than 5% by weight, particularly 7 to 40% by weight, based on the solid content of the conductive treatment liquid.

The amount of conductive fine powder impregnated into the urethane foam is
Although it varies depending on the desired conductivity, it is preferably 7 to 60% by weight based on the foam weight.

In addition, in the present invention, it is possible to adjust the balance between the ease of inserting the IC lead frame and the difficulty in removing it, that is, the
In order to improve the packaging and packing workability, the following - Formula (1) % Formula %) (1) (In the formula, A is K, Na or Ca, B or C is Fe
(II), Fe (DI) , Mn, Al, Mg or V, D is Si or 11) is used.

As mica, the formula (K, Na, Li) (ACMg, V
)! (S i, Al) a O+o (OH) t, such as silomites, sericite, sericite, vanadium, illite, etc., or 2K(Mg, Fe(II), Afris)
Chromites represented by (St,Af)40to(OH,O), such as chromites such as black mica, kinunmo, tetsuunmo, and chinwaldunmo, can be used.

Mica has an average particle size of 10 to 50μ from the viewpoint of dispersion workability.
m fine powder is used.

In addition, the amount used is preferably 1M% or more based on the solid content of the conductive treatment liquid in order to achieve the above-mentioned effect. Although it improves workability, it also has the disadvantage of being too easy to come off, so the upper limit of its usage is preferably 50% by weight or less based on the solid content of the conductive treatment liquid.

In the present invention, a conductive fine powder and a fine mica powder represented by the general formula (1) are dispersed in water together with a nonionic surfactant having an HLB of 12 or more using a homo mixer or a Despa mixer. Prepare the liquid.

If foaming occurs during the preparation of the dispersion, it is recommended to add a small amount of an antifoaming agent, such as a silicone resin emulsion. .

The conductive treatment liquid of the present invention is obtained by dispersing a water-dispersible binder and a nonionic surfactant having an HLB of 8 to 11 in the thus prepared dispersion.

As the water-dispersible binder, various latexes, emulsions, hydrosils, etc. can be used, but it is preferable to use a binder that firmly fixes the conductive fine powder with a urethane foam.In particular, from the viewpoint of durability, a binder that can be self-crosslinked or externally crosslinked is preferable. is preferred.

Examples of the self-crosslinkable binder or externally crosslinkable binder include latexes and emulsions such as polyacrylic esters, modified acrylic esters, acrylic styrene copolymers, and vinyl acetate/acrylic copolymers.

The water-dispersible binder is preferably used in an amount of 50 to 90% by weight based on the solid content of the conductive treatment liquid.

The conductive treatment liquid of the present invention includes a nonionic surfactant with HL'B of 8 to 11 (hereinafter sometimes referred to as "penetrating agent").
By containing the urethane foam, the conductive treatment liquid can be quickly and uniformly permeated into the urethane foam, and variations in the conductivity of the urethane foam can be eliminated.

Even if it is a nonionic surfactant, the HLB is less than 8 or 1.
If the value exceeds 1, this effect cannot be fully exhibited. Furthermore, since the ionic surfactant also has a large foaming power, it is difficult to achieve a uniform impregnation effect on the urethane foam with the conductive treatment liquid.

Examples of the nonionic surfactant having an HLB of 8 to 11 include polyethylene glycol alkyl phenyl ether and polyethylene glycol alkyl ether.

The amount of nonionic surfactant with HLB of 8 to 11 is:
It is preferably 0.1 to 5% by weight, particularly 0.5 to 2% by weight in the conductive treatment liquid. If it is less than 0.1% by weight, there is almost no effect, and if it exceeds 5% by weight, the effect will be saturated, and problems such as stickiness may occur instead.

In particular, when aging treatment is performed while the IC lead frame is stuck in the conductive urethane foam, the IC lead frame may be corroded due to the heat treatment due to the conductive urethane foam. In order to prevent this, it is preferable to include a rust preventive agent in the conductive treatment liquid.

As the rust preventive agent, urea, a mixture of sodium nitrite and mono(or di)ethanolamine benzoate, dicyclohexylammonium caprylate, diisopropylammonium nitrite, benzotriazole, and the like can be used. The amount used is not particularly limited, but it is preferably 1% by weight or more, particularly 2 to 10% by weight based on the solid content of the conductive treatment liquid, from the viewpoint of the effect and its sustainability.

This conductive treatment liquid can be prepared by adding a water-dispersible binder and a nonionic surfactant having an HLB of 8 to 11 to the dispersion liquid.

A conductive urethane foam can be obtained by impregnating urethane foam K with the conductive treatment liquid thus prepared, for example using a roll, and drying it in a hot air oven.

In the present invention, since a nonionic surfactant with an HLB of 12 or more is used, the conductive fine powder and the mica fine powder are uniformly dispersed in the conductive treatment liquid.
(Since we use a nonionic surfactant with an LB of 8 to 11 to penetrate into the interior, the urethane foam treated with the treatment liquid is uniformly coated with conductive fine powder and mica fine powder. It is possible to obtain a urethane foam that is dispersed, has no conductive nickel, and has a well-balanced property of ease of insertion into IC lead frames and resistance to removal.

Furthermore, since the conductive treatment liquid contains a water-dispersible binder, the conductive fine powder is firmly fixed to the urethane foam.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

Examples 1 to 4 and Comparative Examples 1 to 6 Carbon black (particle size 46 mμ
, C0NDUCTEX 950 BEADS, :]
(manufactured in Japan), graphite (particle size 44
μ, T44, manufactured by LONZA LTD), potassium matahachitanate whiskers (fiber diameter 0.2 to 0.5 μ, Dentol WK-200B, manufactured by Otsuka Chemical ■) were used, and a conductive treatment solution was prepared at the mixing ratio shown in Table 1. and have a density of 2
A urethane foam with a weight of 0 kg/Po, a thickness of 10 mm, and a width of 1 m was continuously impregnated with a roll and dried at 120° C. for 20 minutes to obtain a conductive urethane foam.

The evaluation results are shown in Table 2.

The evaluation method is as shown below.

The state of adhesion of the conductive fine powder was observed by visually observing the cross section of the conductive urethane foam obtained after impregnation.

The resistance value over 1 cm of the surface of each plate of conductive urethane foam was measured using a tester.

[1 c in the center of the cross section of the conductive urethane foam obtained
The resistance value between m was measured using a tester.

Conductive urethane foam with standing ductility 5C11X5C1+1
(thickness: 10 m+) were placed on top and bottom of a copper plate and treated in a gear oven at 100° C. for 72 hours under a load of 200 g, and the degree of discoloration of the copper plate was visually observed.

O: No discoloration Δ: Slight discoloration ↓ [A hybrid IC was inserted into the obtained conductive urethane foam, and the ease with which it was inserted was observed.

○: Good ×: Earthworks that are difficult to stick in” dυζ (A hybrid IC was stuck in the conductive urethane foam obtained, and the IC was shaken with the stuck side facing down, and the removal of the hybrid IC was observed.

○; Pulling does not fall Δ; Pulling does not fall off ×; Pulling falls off [Effects of the Invention] According to the present invention, the adhesion of the conductive material and the variation in conductivity are improved, and the IC lead frame becomes easier to insert and A conductive urethane foam with a well-balanced resistance to coming off can be provided, and this conductive urethane foam can be widely used for wrapping, packaging, and transporting electronic device parts.

Claims (2)

[Claims] (1) Conductive fine powder using a nonionic surfactant with an HLB of 12 or more and the following general formula (I) A (B, C)
_2_〜_3D_4O_1_0(OH,F,O)_2・
...(I) [wherein A is K, Na or Ca, B or C is Fe
(II), Fe(III), Mn, Al, Mg or V,
(D represents Si or Al) into a dispersion of fine mica powder expressed in water,
A conductive urethane foam obtained by dispersing a water-dispersible binder and a nonionic surfactant having an HLB of 8 to 11 to prepare a conductive treatment liquid, and impregnating and fixing the same into a urethane foam. (2) The conductive urethane foam according to claim 1, wherein the conductive treatment liquid contains a rust preventive agent.