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Durable water-absorbent&quick-dry SRagent

1. Introduction

If synthetic fiber, such as polyester, has more hydrophilic properties, especially water/perspiration absorbency with wash-fast resistance, its use will further broaden.

Meanwhile, cases of cellulosic fiber, which originally possesses great water absorption, turning water-repellent have become frequent recently, resulting from the use of complex finishing composites (e.g. fixing agents, resins, softening agents etc) inhibiting the hydrophilic properties of fiber.

Superior hydrophilic properties (water/perspiration absorbency) will allow varieties of fiber materials, knits, wovens and industrial materials a broader scope of use. Gingham shirting, bedding, knits, toweling, sportswear, casual wear, upholstery, sheeting and table linens are some examples.

Here, the use of a 'durable, water-absorbent & quick-dry SR finishing agent', i.e. a fiber finishing auxiliary capable of a) inhibiting degradation of hydrophilic properties due to repeated home laundering, b) repelling oil and c) soil release (SR) during laundering, will result in the creation of products of high practicality with a broader scope of use.

While the traditional rendering of oil/water-repellent 'SR', for which fluorocarbon polymer is mainly used, stood for the effect of inhibiting oil adhesion, the practical meaning is rather soil-repellent, soil-proofing, soil-guard or soil-resistance.

Originally, the idea of SR finishing was to impart some hydrophilic properties to highly-hydrophobic polyester in order to prevent soil adhesion, especially oil stains, and to produce a fiber surface with oil-release properties.

When hydrophobicity is high, the charging tendency becomes strong, soil adhesion more likely and, ultimately, a stain-darkened material will result. Oil stains also adhere heavily, which makes their removal and washing off difficult.

Taking the above points into consideration, the surface treatment with sufficient hydrophilic properties will bring out the following advantages:

●Water/perspiration absorbency
●Easy oil removal, improved SR and OR (oil-release) properties
●Improved anti-static properties

The use of polymers and chemical compounds other than fluorine-based polymer can also be considered for water absorbent SR. In addition, since the kind of oil staining and the oil concentration often vary, oil-releasing results will differ.

Thus, the application of many different types of hydrophilic stain-resistant agent should be taken into consideration.

This article will deal with two unique products, developed by Kotani Chemical Industry with a view to the multiple purposes mentioned above.

■ Queenstat NW-Econc
Water-absorbent, quick-dry, wash-fast anti-staining SR (OR) and softener for polyester

■ Queenset PSO-5500
Durable water-absorbent anti-static SR, hydrophilic improver for all kinds of fiber, including cotton and polyester

The features of the two products are compared in Table 1.

Textile-finishing polymers are mainly concerned with the development of such products, however, it is also important to know from what chemical substances we need to select an oil-repellent component and an oil-releasing component. The use of a hydrophilic type as the main chain and the selection of copolymerizing, bond-reacting groups from hydrophilic groups will be called into account, as well as the addition of a water-absorbent and a cross-linking groups. A functional group (polymer) formed in this manner needs to be predetermined to act as a stronger cross-link with or a strengthener of adhesion to the fiber materials.

Based on the standpoint above, a short account of some proposals is given in the next chapter.

2. Outline of durable, hydrophilic SR agent

Figure1 Example of durable,water-absorbent SR agent structure

Some proposals are indicated in Figure 1. First of all, for the skeletal, principal chain structure of polymer, a selection should be made from the vinyl group, water-absorbent silicone, isocyanate (urethane), polyester polymer, polyamide, fluorocarbon polymer and the epoxy group in order to attain hydrophilicity to the fullest extent possible. The structure then is bound, combined, or reacts with another hydrophilic group, for which the incorporation of a cross-linking group or a hydrophilic moisture-retentive component will work effectively.

In general, as hydrophilic groups there are ethylene glycol, diethylene glycol, triethylene glycol, alkylene oxide polymer, PEG, PPG, PEG block polymer, polyether, glycerin, sorbitol etc.
For uses also as a cross-link, both end-terminal groups of chemical compounds should take the form of the vinyl, glycidyl or allyl groups before application.
Squalane, chitosan, hyaluronic acid, collagen, sericin, natural protein, cellulosic substances and thickeners are regularly used as moisture-retentive components.

○Hydrophilic vinyl-polymer in Figure 1 Various devices will be possible based on Figure 2-1, which shows an example of incorporating an acrylic acid copolymer to each hydrophilic group. Durability will be added and stains can be removed easily. Chemicals listed have been long used as bases for practising anti-staining techniques.

○Water-absorbent silicone which carries reactive groups already possesses in its structure cross-linking and hydrophilic properties and is also capable of producing soft hand. Since it can cross-link with other hydrophilic groups, it is highly valued for use in a durable, water-absorbent finishing agent or as an SR agent (see Figure 1 and Figure 2-2).

Figure2 Examples of durable,water-absorbent SR agent structure

○By incorporating an etherizing compound, a polyether, alkoxylating compound to diisocyanate, polyurethane with high hydrophilic properties can be obtained. It is a very interesting cross-linking polymer which allows the formation of a highly durable polymer by cross-linkage between hydrophilic groups and polyurethane, binding of fluorine alcohol, as shown in Figure 2-3, or copolymerizing of hydrophilic vinyl groups.

○Since a hydrophilic polyester resin polymer skeleton is one that displays highest affinity to polyester, it is used as a base in a wash-fast & water-absorbent SR agent for polyester in the form of polymer such as PEG with improved hydrophilic properties. Nowadays, it is often used as a high function compound, bound or mixed with melamines, cationic silicones, block isocyanates, and hydrophilic group compounds as shown in Figures 1 and 2-4.

○As fluorine groups are fundamentally based on acryl or methacrylic acid type vinyl groups, they are often copolymerized, as shown in Figures 1 and 2-5, with:

●diisocyanates (urethane adducts)
●hydrophilic groups (PEG with cross-linking group)
●acrylates, vinyliden chlorides etc

or, their adhesive properties can be strengthened with fluorine alcohol, amide and PEG, or cross-linking resin polymer, their use is highly valued as oil-release properties can be attained from a hydrophilic group, and oil-repellency from a fluorine-group chain.

○Polyamide polymer and epoxy polymer are convenient polymer groups that allow a wide range of applications such as below.

●Incorporation of a hydrophilic group using carboxylic acid
●Use of an epoxy grouop as a cross-linking agent
●opolymerization with a functional polymer
●Use as an interactive cross-linking

Although the above is an overview that would only scratch the surface, crucial basics have been included.

In the following chapters 3 and 4, a description of the products, developed based on our long-accumulated research data, will be given with references to Figures 1 and 2.

3. Queenstat NW-Econc

This is a wash-fast, water-absorbent, quick-dry, anti-stain SR agent/softener for polyester.

The addition of durable hydrophilicity to polyester and its blends will bring about durable anti-static properties, facilitate removal of oil stains and therefore result in superior oil-release properties. This product, which also works as a softener other than giving SR properties, is an agent capable of upgrading polyester with multiple functions.

Having different uses and application areas from water/oil-repellent SR finishing, it allows a considerably wider scope of application as mentioned earlier.

This is a hydrophilic polymer which displays strong adhesive properties to polyester, and the performance of treated fabric will not deteriorate even after 10 launderings. In brief, it imparts to PET, E/C and E/R fibers the following properties:

(1) Durable water absorbency, quick-dry, SR, and easy oil-stain removing OR properties during laundering
(2) Hydrophilic and anti-static properties
(3) Soft hand, smoothness and flexibility
(4) High fastness to washing, with minimal deterioration due to home laundering

It forms a highly-durable film on the fiber surface by undergoing padding, drying and curing treatments (150-180°C x 30sec.).

Oil stains could be heavy oil, motor oil, lubricant, grease, spice oils, butter, mayonnaise, ketchup, vegetable oils, lipstick etc, all very hard to remove, however, stains on fabric treated with Queenstat NW-E wash out easily by washing and the effect (OR properties) will not deteriorate even after repeated washes.

Table 2 shows the characteristics, effects and physical properties (appearance, pH and ionicity) of Queenstat NW-E with directions for use.

Table2 Characteristics, performances, physical properties and directions for use

It is an extremely convenient finishing agent which can easily be combined with other chemicals without causing yellowing, color alteration, or any factors that will degrade dyeing fastness.

Figure 3 shows the water absorbency (150mm in 10 min.) and the oil-removing properties of NW-E-treated polyester tropical cloth, padded with 3% NW-E solution and then dried. The initial performance is maintained after 1, 5 and even 10 washes.

 

Note: Home laundry detergent: 1.5g/L
45°C x 5min
A cycle of cold rinsing -dehydration-drying counted as 1 wash

○Water absorbency: 150mm (10min) at the beginning and 130mm (10min) after 10 washes

○Durable OR properties indicated in the performance index of 90 after 10 washes, as opposed to the initial 100

NW-E's performance is rated highly as both the water absorbency and oil release properties remain poor in the untreated fabric.

Figure 3 Performance of Queenstat NW-E treated cloth《wash-fast water absorbency, oil-removal》

In Picture 1, water absorbency is compared before and after 10 washes in vertical wicking distances (cm/10 min.) of dye liquor absorption in fabric (polyester) padded with NW-E 3% solution, dried and cured (180°C x 30 sec).

From this, it is clear that the untreated cloth has practically no water absorbency, while the treated fabric maintains significantly higher water absorbency even after 10 washes.

Picture 1 Comparison of water absorbency of Queenstat-treated cloth and untreated before and after washing

4. Queeenset PSO-5500

This is a wash-fast water-absorbency improver which functions effectively with all kinds of fiber material, including cotton, cellulose, synthetics (polyester, nylon, acryl etc), blends and union cloths.

In combined use in the durable water-absorbent, anti-static finishing of synthetic fiber, or with other chemicals and finishing auxiliaries (resins, cationic surfactants, softeners, silicone softeners and fixing agents) which turn natural fiber water-repellent, Queenset PSO-5500 will be effective in degrading water repellency, upgrading water absorbency and penetration. Moreover, it is suitable for all treatments that require durable, high water/perspiration-absorbent finishing.

(1) Superior wash and dry cleaning fastness without color alteration, yellowing, or deterioration in fastness

(2) Superior compatibility with resins, catalysts, fluorescent brighteners and finishing agents, with good in-bath stability
(3) The addition of potent water absorbency results in improved oil repellency and easier oil release (SR, OR).
(4) Imparts soft hand

Table 2 is an outline of the characteristics and physical properties of PSO-5500 with directions for use.

In the evaluation of water absorbency, the following two points need to be considered: 

●The speed of water absorption (sec)
●The amount of water absorbed within given time (water absorption)

The speed of water absorption is important and can be figured by measuring the time (sec) it takes for a drop of water on a fabric surface to be absorbed completely.

Figure 4 compares speed of water absorption before and after 50°C x 30 min washing (drying) of PET, cotton and E/C blend fabric, each padded with Queenset PSO-5500, dried and cured.

Figure4 Water absorption speed of Queenset PSO-5500 according to the type of fiber

Even fabric with virtually no water absorbency in its original state absorbs water instantaneously or within a few seconds after treatment with PSO-5500. Some deterioration due to washing can be recognized, however, superiority to our competitors' products is significant as the absorption is instantaneous in cotton and takes around 50 seconds in synthetics.

The indication of "Rf-combined" for cotton broad in Figure 4 denotes combined use of the resin finishing solution (10% glyoxal resin + 3% catalyst).

Figure 5 shows water absorbency measured in the vertical wicking distance (cm) of a given period of time (10 min) from the bottom of the PSO-5500 treated cloth.

Figure5 Queenset PSO-5500 wash-fast water absorbency

Water absorbency deteriorates in cotton due to resin treatment (Rf: 10% glyoxal resin + 3% catalyst, padding-drying-curing). However, the water absorbency improved considerably with 3% PSO-5500 added in the resin finishing bath, and equally superior performance was maintained even after 5 washes.

Similar effects can be expected in polyester, as shown in the result of treatment with 3%

 PSO-5500 alone in Figure 5.

The extremely poor water absorbency in the untreated polyester was remarkably improved, and without any deterioration after 5 washes.

5. Conclusion

The basic technical factors of wash-fast hydrophilic, water-absorbent, quick-dry SR finishing agents were discussed outlining from components to practical examples, and data on our two unique products were also presented.

Increases in use and applications make a product more versatile, for which an economical composition structure will be the primary requirement.

If it is difficult to produce a wide-ranging SR function, targeting limited functionality will also be a possibility.

Broadening of use and applications in this area is much anticipated, along with further progress in technology development.

KOTANI CHEMICAL
13-14, CHIKKO HAMADERA NISHI MACHI, NISHI-KU, SAKAI CITY, OSAKA 592-8352, JAPAN
Phone:+81 72 268 0291
FAX   :+81 72 268 0293
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