Molded antimicrobial article and a production process thereof

Details Molded antimicrobial article and a production process thereof Molded antimicrobial article and a production process thereof

1999-04-23

2002-02-05

Dees, Jose′ G. (Department: 1616)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Wearing apparel, fabric, or cloth

C424S402000, C424S405000, C424S406000, C424S443000, C428S357000

Reexamination Certificate

active

06344207

ABSTRACT:

TECHNICAL FIELD
The present invention relates to molded antimicrobial articles, particularly antimicrobial fibers excellent in industrial washing durability, and a production process thereof.
BACKGROUND
Molded antimicrobial articles, especially fibers, are widely used for various clothes, interlinings, linings, bedclothes, interior products and the like. These fibrous products are excellent in antimicrobial activity and, by various improvements, have become good in household water washing durability.
However, in recent years, occurrences of infection in hospitals due to methicillin resistant Staphylococcus (MRSA) has become a problem. As a countermeasure, white overalls, covers, sheets, curtains and the like have been treated in an attempt to impart antimicrobial characteristics. However, these fibrous products for use in hospitals are usually very frequently industrially washed at 60 to 85° C., and few conventional techniques provide sufficient durability against such washing.
Fibers have been treated to impart antimicrobial characteristics by blending an inorganic antimicrobial agent such as silver, copper or zinc into synthetic fibers at the spinning stage, or by applying an organic antimicrobial agent such as a quaternary ammonium salt by spraying or padding in a post-treatment. The former method is excellent in view of washing durability, but does not permit antimicrobial treatment at a later stage. Furthermore, the antimicrobial agent precipitates as crystals on the spinneret face during spinning to cause frequent fiber breaking and the like, which is a problem in the yarn production process. On the other hand, the latter method is poor in washing durability of antimicrobial activity, although it advantageously allows antimicrobial treatment in a later stage.
JP-A-61-239082 describes treating N6 socks in a pyridine based antimicrobial agent suspension at 130° C. for 60 minutes with shaking. However, when a suspension is used, the particle size of the antimicrobial agent is too large to obtain a sufficient effect. Furthermore, JP-A-09-273073 describes treating polyester fibers with a pyridine based antimicrobial agent simultaneously with dyeing, but the antimicrobial agent used is not proper and does not provide a sufficient effect.
Accordingly, it is highly desirable to provide a molded antimicrobial fibrous product excellent in industrial washing durability and a production process thereof.
SUMMARY OF THE INVENTION
The present invention relates to a molded antimicrobial article, comprising an infiltrated antimicrobial agent which forms independent phases of 0.01 &mgr;m or more in short diameter in the molded article. It is preferable that a pyridine based antimicrobial agent with a molecular weight of about 200 to about 700 and an inorganic property/organic property value of about 0.3 to about 1.4 forms independent phases of about 0.01 &mgr;m or more in short diameter in the molded article, and that about 50% or more of the antimicrobial agent is infiltrated to a depth range of about 0.5, preferably, about 1 &mgr;m or more from the surfaces of fibers, or about 30% or more of the antimicrobial agent is infiltrated to a depth range of about 2 &mgr;m or more from the surfaces of fibers. It is also preferable that the molded articles are fibers, that the surface area used per 1 g of fibers is about 0.1 m
2
or more, and that the synthetic fibers are a colored antimicrobial fibrous product.
The molded antimicrobial article of the invention can be obtained, for example, by immersing a fibrous product in a dyeing liquid containing a pyridine based antimicrobial agent with a molecular weight of about 200 to about 700, an inorganic property/organic property value of about 0.3 to about 1.4 and an average particle size of about 2 &mgr;m or less and, preferably, treating simultaneously with dyeing under pressurization.
As another embodiment, the antimicrobial article can also be obtained by applying a liquid containing the same pyridine based antimicrobial agent to a fibrous product by padding or spraying, and heat-treating at about 160 to 200° C. in a dry or wet state.
DETAILED DESCRIPTION OF THE INVENTION
It will be appreciated that the following description is intended to refer to specific embodiments of the invention selected for illustration and is not intended to define or limit the invention, other than in the appended claims.
A preferable antimicrobial agent used in the present invention has a molecular weight of about 200 to about 700, an inorganic property/organic property value of about 0.3 to about 1.4 and an average particle size of about 2 &mgr;m or less.
A pyridine based antimicrobial agent is stably infiltrated and diffused into a molded article, especially synthetic fibers and synthetic resin films. The molded article can also be of any other form such as a film, sheet, plate or rod. However, for the sake of simplicity, this description is limited to cases of fibers. We have discovered that the antimicrobial agent dispersed in the molded article shows behavior similar to that of the disperse dye if the antimicrobial agent is particularly selected to be closer to the disperse dye in three requirements: molecular weight, inorganic property/organic property value and average particle size.
However, it is surprising that the solid antimicrobial agent forms independent phase of about 0.01 &mgr;m or more in “short diameter” inside the fibers, and that about 50% or more of the antimicrobial agent is infiltrated to a depth range of about 0.5, preferably, about 1 &mgr;m or more from the surfaces of the fibers or that about 30% or more of it is infiltrated to a depth range of about 2 &mgr;m or more from the surfaces of the fibers. “Short diameter” as used herein means the number average diameter of independent phases taken through a cross section of the fiber.
It is not clearly understood that the antimicrobial agent can be diffused as particles in the highly crystalline and structurally dense fibers. However, without being bound by any particular theory, we believe that the antimicrobial agent is dispersed as, respectively, single molecules or groups consisting of several cohesive molecules, to be precipitated which forms independent phases of agent in the particles in the fibers. As for the diffusion degree of the antimicrobial agent, if the distance from the fiber surface to the center of the fiber section is set at 1, the antimicrobial agent is infiltrated and diffused into the fiber at least a distance of about 0.2. As for the concentration distribution of the antimicrobial agent, the ratio of the concentration of the antimicrobial agent existing in a range from the center of the fiber section to a distance nearest to the center of the fiber section to the concentration of the antimicrobial agent existing in a range from the center of the fiber section to the surface is about 1:1 to about 1:10. Thus, the antimicrobial agent is sufficiently infiltrated inside the fibers. Unless these conditions are satisfied, the antimicrobial agent is not properly diffused into the synthetic fibers, and sufficient industrial washing durability cannot be obtained.
Washing durability is low if the molecular weight of the antimicrobial agent is less than about 200, even when the antimicrobial agent is infiltrated and diffused into the synthetic fibers. On the other hand, the antimicrobial agent is not infiltrated into the synthetic fibers if its molecular weight is more than about 700. It is preferable that the molecular weight of the antimicrobial agent is about 300 to about 500.
The “inorganic property/organic property value” referred to in the invention is a value defined by Minoru Fujita for expressing the polarity of various organic materials [Revised Edition, Science of Chemical Experiments—Organic Chemistry—Kawade Shobo (1971)]. Specifically, it is a ratio of the sum of inorganic property values to the sum of organic property values obtained from the inorganic property values and organic property values of various polar groups shown in Table 1 with the organic property va

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