Cellulose fiber-containing structure

Details Cellulose fiber-containing structure Cellulose fiber-containing structure

2000-04-03

2003-04-01

Gupta, Yogendra N. (Department: 1751)

Bleaching and dyeing; fluid treatment and chemical modification

Chemical modification of textiles or fibers or products thereof

C008S116100, C427S002310, C427S389900, C427S392000

Reexamination Certificate

active

06540792

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cellulose fibers-containing structure having shape stability and antimicrobial property excellent in industrial washing durability.
2. Description of Related Arts
Antimicrobial fiber structures are widely used in various clothes, interlinings, linings, bedclothes, interior products, etc. Especially in recent years, the intra-hospital infection by Methicillin Resistant Staphylococcus Aureus (MRSA) poses a problem, and as a countermeasure, white overalls, covers, sheets, curtains, etc. are desired to be antibacterial against MRSA.
However, since materials used in this area are frequently industrially washed usually at 60 to 85° C., few conventional techniques can provide those having sufficient durability. Furthermore, if those materials contain cellulose fibers, they have a problem that the shape stability becomes poor after washing.
As conventional antimicrobial treatment, it has mainly been practiced to knead an inorganic antimicrobial agent containing silver, copper or zinc, etc. into synthetic fibers in the stage of spinning as described in Japanese Patent Laid-Open (Kokai) No. Hei9-273073, or to spray or pad an organic antimicrobial agent containing a quaternary ammonium salt, etc. as described in Japanese Patent Laid-Open (Kokai) No. Hei4-11076. The former technique is excellent in view of washing durability, but does not allow fabrics such as woven fabrics and knitted fabrics to be treated. Furthermore, since the antimicrobial agent is precipitated as crystals on the die face in the stage of spinning, there is a problem that yarn breaking occurs often. On the other hand, the latter technique has an advantage that fabrics can be treated to be antimicrobial, but is inferior in view of washing durability of antimicrobial property.
Furthermore, in the applications as described above, fabrics with high cellulose fiber contents are preferably used since they have high water absorbability and are agreeable to the touch, but on the other hand, they have such disadvantages that they are likely to be creased and shrunken by washing compared to synthetic fiber structures and that it is difficult to let them have antimicrobial property durable against industrial washing. These disadvantages are desired to be overcome.
SUMMARY OF THE INVENTION
The object of this invention is to provide a cellulose fibers-containing structure having antimicrobial property excellent in industrial washing durability, and also having shape stability such as crease resistance and shrinkage resistance.
The constitution of this invention is as follows.
A fiber structure comprising cellulose fibers crosslinked by using a crosslinking agent and synthetic fibers, characterized in that the crosslinking index represented by the following formula of the cellulose fibers is in a range of 1 to 4, and that the synthetic fibers contain an antimicrobial agent having an inorganic value/organic value ratio of 0.3 to 1.4.
Crosslinking index=
A−B
where A is the coefficient of moisture absorption of the fiber structure after crosslinking in an atmosphere of 30° C. and 90% RH (%), and B is the coefficient of moisture absorption of the fiber structure after crosslinking in an atmosphere of 20° C. and 65% RH (%).
Furthermore, it is preferable that the cellulose fibers are crosslinked and modified by using a specific nitrogen-containing polyfunctional compound, and that the synthetic fibers have a pyridine based antimicrobial agent fixed and exhausted into the fibers.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The cellulose fibers-containing structure referred to in this invention can be not only a fabric but also a band, string, thread, etc. respectively formed by fibers. It can have any structure and shape, but a fabric, i.e., a woven fabric, knitted fabric or nonwoven fabric respectively containing cellulose fibers is preferable.
The cellulose fibers in this invetnion include natural cellulose fibers such as cotton, hemp and pulp, regenerated cellulose fibers such as viscose rayon, etc.
In this invention, the cellulose fibers are crosslinked and modified by a crosslinking agent. The crosslinking agent refers to a compound which reacts with the hydroxyl groups in the cellulose molecules constituting the cellulose fibers, particularly the hydroxyl groups in an amorphous region causing creasing and shrinkage at the time of washing, for forming a crosslinked structure across and in the cellulose molecules. The crosslinking agents which can be used include formaldehyde, dimethylolethyleneurea, dimethyloltriazine, dimethyloluron, dimethylolglyoxalmonouren, dimethylopropyleneurea, cellulose reactive resins obtained by methoxylating or ethoxylating some or all of the methylol groups of these compounds, polycarboxylic acids, isocyanates, etc. Among these crosslinking agents, for efficiently and effectively crosslinking and modifying cellulose fibers, formaldehyde or a nitrogen-containing polyfunctional compound represented by the following general formula (I) can be preferably used.
where R
1
and R
2
denote, respectively independently, —H, alkyl group with 1 to 4 carbon atoms or CH
2
OR
7
; R
3
, R
4
, R
5
and R
6
denote, respectively independently, —H or —OR
8
; and R
7
and R
8
denote, respectively independently, —H or alkyl group with 1 to 4 carbon atoms.
As for the modification degree of cellulose fibers, the crosslinking index defined by the following formula must be in a range of 1 to 4. A preferable range is 2 to 3.5. The crosslinking index is calculated by subtracting the value of the coefficient of moisture absorption of the crosslinked and modified cellulose fibers in an atmosphere of 20° C. and 65% RH from the value of the coefficient of absorption in an atmosphere of 30° C. and 90% RH, and it is an index for knowing how far the cellulose fibers are crosslinked and modified. That is, the index uses that the hydroxyl groups in the cellulose molecules are blocked by crosslinking modification to lower the coefficient of moisture absorption. The smaller the index, the larger the degree of crosslinking modification, and the larger the index, the smaller the degree of crosslinking modification. Generally, the crosslinking index of unprocessed cotton and hemp is about 4 to 5.
Crosslinking index=
A−B
where A is the coefficient of moisture absorption of the fiber structure after crosslinking in an atmosphere of 30° C. and 90% RH (%), and B is the coefficient of moisture absorption of the fiber structure after crosslinking in an atmosphere of 20° C. and 65% RH (%).
If the crosslinking index is smaller than 1, the crosslinked structure is formed excessively to lower the strength and flexibility of the fabric, and though the fabric is good in shape stability, it cannot be practically used. On the other hand, if the crosslinking index is larger than 4, the crosslinking modification of cellulose fibers is insufficient, and the required level of shape stability such as crease resistance and shrinkage resistance cannot be imparted. Considering the balance among the strength, flexibility and shape stability of the fabric, it is preferable that the crosslinking index is in a range of 2 to 3.5.
The nitrogen-containing polyfunctional compound refers to a compound having nitrogen and two or more functional groups. The compounds which can be used here include, for example, dimethylolethyleneurea, methylated dimethyloluron, dimetlylolpropyleneurea, dimethyloldihydroxyethyleneurea, 4-methoxy-5-dimethylpropyleneurea dimethylolation product, methylated trimethylolmelamine, dimethylolalkyltriazones, dimethylolurea, hexamethylolmelamine, tetramethylolacetylenediurea, etc.
For adding any of these crosslinking agents to cellulose fibers, any of various means can be applied. Particularly, the crosslinking agent can be applied as a gas, or by padding, immersion, spraying, printing, coating, gravure processing or foam processing, etc. When the crosslinking agent is a cellulose reactive resin, polycarboxylic acid or isocyanate, etc., pad

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