JPS599254A - Production of nonwoven fabric containing fine hollow bodies - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION When manufacturing fiber reinforced plastics by impregnating a fibrous base material with a resin such as an unsaturated polyester resin, the present invention
The present invention relates to a method for producing a nonwoven fabric used as a fibrous wiper.

Conventionally, nonwoven fabrics containing microscopic hollow bodies have been used as this type of nonwoven fabric. This is to reduce the amount of resin to be impregnated and to economically obtain fiber reinforced plastics. Therefore, the more microscopic hollow bodies are contained in the nonwoven (Ii), the more economically fiber-reinforced plastics can be obtained.

However, in the conventionally used nonwoven fabrics, the volume of micro hollow bodies was about 21 L, which is about 50% of the body volume. From the above-mentioned economic point of view, it is desirable to include a larger amount of micro hollow bodies and increase the volume of the micro hollow bodies included in the volume of the nonwoven fabric. However, when the volume exceeds 50 and is about 60% by volume, there are disadvantages in that resin impregnation becomes poor and the strength of the nonwoven fabric itself decreases. This is due to the reason described in F below.

Traditionally, staple fibers have been used to produce nonwoven fabrics. Staple fibers are single fibers mainly used for spinning, and generally have a crimp count of 3 or more per cm, but a crimp retention of less than 60%. In order to obtain a nonwoven fabric having a certain strength using such staple fibers, a certain fiber density is required. This is because fiber is required. Therefore, in nonwoven fabrics that require a certain degree of opacity, the amount of microscopic hollow bodies contained therein is naturally limited. If the microscopic hollow bodies are contained beyond this limit, the gap between the microscopic hollow bodies and the staple fibers will become very fine, and the resin tit with a certain viscosity will not enter into the fine gap.
As a result, the impregnating properties of the resin are poor. On the other hand, it contains more micro hollow bodies and is a staple.

If the fiber density of the nonwoven fabric is reduced in order to increase the gap between the fibers and the micro hollow bodies to some extent, the strength of the nonwoven fabric will decrease, as is clear from the above, and the 6'( It is not suitable for use with J fat-impregnated wrapping material and 17.

Therefore, as a result of various studies, the present inventors found that a nonwoven fabric manufactured using single fibers and microspheres that have a high degree of crimp retention is
Despite containing a large amount of microscopic hollow bodies, the gap between the single fibers can be maintained relatively large, and the strength of the nonwoven fabric makes it unsuitable for use as a base material for fiber plastics. The inventors have discovered that the temperature does not decrease to a certain extent, and have come up with the present invention.

That is, the present invention has a number of crimps of 3 or more and a crimp retention of 6.
A fibrous web containing at least 20% of monofilaments of 0% or more is prepared, and then the outer wall is heated to
A liquid mixture of microspheres made of a thermoplastic resin and containing a thermally expandable substance and a binder is applied to the fiber web, and then heated to dry the liquid mixture, 17 at the mother contact point of the fiber phase force that constitutes the fiber web! , 1 ai' binder is fixed, and the previous gI
! The present invention relates to a method for producing a nonwoven fabric containing microscopic hollow bodies, characterized by softening the outer wall of the microsphere and expanding the thermally expandable material to substantially increase the volume of the microsphere.

Here, microspheres refer to those in which the thermally expandable material contained inside is not yet substantially covered with KrMl.
The micro hollow body refers to the state after being substantially expanded.

The single fibers used in the present invention can be of any type, including natural fibers, semi-synthetic fibers, and synthetic fibers.

However, when the number of crimps is 3 or more/cM, the crimping retention IM is 60.
It must be 'Takui'2. Here, the number of crimp t is measured by J18, L-1074 method! The crimp retention is the ratio of the residual crimp rate to the initial crimp rate measured by the same method, expressed as (%).

When the number of crimps is less than 3/c, the gaps between the #a fibers in the fabricated fibrous web become small, making it difficult to contain many microspheres. The single fibers themselves lose their bulk, and as the fiber density increases, the gaps between the fibers become as small as possible. Also, crimp retention is 60%.
If the fibers are too thin, physical external force is applied at the stage of opening the monomolecular fibers, and crimp tends to disappear at the stage of forming the fiber web, which is not preferable.

When the crimp disappears, the bulk of the fiber itself disappears,
This is because the gaps between the constituent fibers become smaller.

R+31RN ik 3 pieces/cm or more, crimp retention 60
It is sufficient that the single fibers are contained in the fiber web in an amount of 20% or more by weight. If it is less than this, the gap between the constituent fibers cannot be maintained at an appropriate size, so it is not preferable. Stable fibers for spinning are usually used as fibers other than the single fibers.

The microsphere consists of an outer wall made of thermoplastic resin and a thermally expandable material contained inside the outer wall.

A typical example is that the outer shell is vinylidene chloride.
An example is an acrylonitrile copolymer in which isobutane is encapsulated.

As a binder, acrylonitrile rubber,
Styrene-butadiene rubber, acrylic resin, natural rubber, etc. are used.

The microspheres and binder are applied to the fibrous web as a liquid mixture, i.e., dispersed in a liquid.

As a method of application, a spray method, a dipping method, etc. are used.

1j] The heating step must be conducted under such conditions that the mixture is dried, the outer wall of the microspheres is softened, and the thermally expandable material is expanded.

Therefore, the heating conditions are determined by the dispersion medium and microspheres used.

By passing through two culms of heating, the binder is fixed to the contact points of the constituent fibers in the fiber web, and the microspheres expand and substantially increase in volume, resulting in a nonwoven fabric containing microscopic hollow bodies. It will be done.

In the present invention, the number of crimps is 3 or more and the crimp retention is 60.
Since the fibrous web is created using more than % of microspheres, the fibers themselves do not lose their bulkiness and the gaps between the constituent fibers are relatively large.Therefore, a large amount of microspheres can be obtained. Even in the case of non-woven fabrics that have been used for a long time, gaps are formed between the small core and the interwoven fibers, and the continuous state of the seven fibers is also good. n1 bulky J
Therefore, it is relatively easy to increase the fiber density without reducing the gap between the constituent fibers. Therefore, the strength of the obtained nonwoven fabric is also small.

As shown in the figure (X-th), it is possible to make the ik 4A of the micro hollow body about 60% by volume per 1 + - product of the non-woven fabric, and it is possible to reduce the amount of resin groups to be impregnated, and also to reduce the amount of resin to the non-woven fabric. Low immersion properties, no 1z loss, reinforced with fibers]
' You can get Rustics.

This will be explained below with reference to embodiments.

Example number of crimp: 4117-1/cm, crimp retention: 3 at 40%
Denier, 64% polyester fiber used for normal spinning, 4 crimp/cm, 14B5% crimp
5 denier, 58 mm polyester fiber 40% by weight
A fibrous web with a basis weight of 78 g/ni' was prepared by uniformly mixing the above.

Separately, a mixed aqueous solution was prepared using polyacrylonitrile as a binder and microspheres containing isobutane and having an outer shell formed of a vinylidene chloride-acrylonitrile copolymer with a weight ratio of 6=4.

The fibrous web was impregnated with the mixed aqueous solution and heated to 135°C in a wide range. Finished non-woven fabric 1J, 1481/
d, thickness 4W blade, strong II: 15 L5+ / 5
It was t:vujJ. In addition, the occupied volume t of the micro hollow body is 60 body volume, and the occupied volume of each constituent fiber is 3% by volume.
The volume occupied by the binder was 1.5% by volume, and therefore the spatial volume of the unlined fabric was 35.5% by volume.

When this nonwoven fabric was impregnated with unsaturated polyester resin, the impregnation was completed in about 40 seconds.

It was found that the impregnating properties were good.

Comparative Example Polyester fiber 100 for normal spinning used in Examples
%, a nonwoven fabric with a space volume of 35.5% by volume was produced under the same conditions as in the example. The strength of this nonwoven fabric is 11y
/5ctn Ill. What's more, when impregnated with unsaturated polyester resin, it took about 100 seconds to complete the impregnation)! ,′,Completed.

Claims (1)

[Claims] A fiber web containing at least 20% by weight of single fibers with a crimp count of 3/1 or more and a crimp retention of 60% or more is created, and then the outer wall is formed of a thermoplastic resin and the inside is made of a thermally expandable resin. A liquid mixture of microspheres containing a substance and a binder is applied to the niI fibrous web, and then heated to dry the liquid mixture, and the mixture is applied to the points of contact between the fibers constituting the fibrous web. A method for producing a nonwoven fabric containing microscopic hollow bodies, characterized by fixing a binder, softening the outer wall of the microspheres, and expanding the thermally expandable substance to substantially increase the volume of the microspheres. ,