GB2068428A

GB2068428A - Disposable article of improved colour, composition and method for making same

Info

Publication number: GB2068428A
Application number: GB8035533A
Authority: GB
Original assignee: Colgate Palmolive Co
Current assignee: Colgate Palmolive Co
Priority date: 1979-11-09
Filing date: 1980-11-05
Publication date: 1981-08-12
Also published as: ZA806744B; GB2068428B; IE802321L; IE50175B1; JPS5692964A; FR2486087B1; GR71714B; AU6424780A; PT72011A; JPS6411668B2; AU537792B2; ES496537A0; CA1145508A; CH647799A5; DK396680A; DE3041682A1; FR2486087A1; BE886073A; MX153471A; PH16635A

Abstract

A mixed dye composition for brightening and whitening cellulose material comprises a first dye having an absorption band from 4800 ANGSTROM to 6000 ANGSTROM and a second dye having an absorption band from 4900 ANGSTROM to 6300 ANGSTROM in a weight ratio of from 10:1 to 1:10. The first dye is the colour index acid violet dye 47 which is an anthraquinone type dye, while the second dye is the colour index acid violet dye 49 which is a triphenylmethane type dye. The cellulosic material is used as an absorbent mass in disposable articles used for capturing body fluids (e.g. diapers, sanitary napkins, and incontinence pads which are generally structured with a top sheet or sheets, a body of absorbent material thereunder and a back sheet to restrain loss or escape of the fluids from the article).

Description

SPECIFICATION Disposable article of improved colour, composition and method for making same The present invention relates to absorbent products which are generally characterised as disposables and among such products are diapers, feminine hygiene pads and incontinence pads and in particular, it relates to improvements in such products employing wood fluff derived from mechanical or thermomechanical pulp. The fluff is used as the primary absorbent mass in these products and reference is made to such recent patents as U.S. Patents 4,069,821; 4,066,081; 4,062,362; 4,060,085; 4,044,768; 4,029,101; 4,029,100 and 4,027,672, wherein wood fluff is employed as an absorbent mass in products of the type contemplated herein.The pulp used to make the fluff in these prior patents has generally been chemical pulp and such fluff is a highly bleached product of a whiteness of about 90 or greater. The standard of 100 (whiteness) is based on a magnesium carbonate surface and is accepted as the criteria for excellent whiteness. Chemical pulp is also advantageous in that one obtains optimum fibre lengths from the wood source thereby leading to absorbent pads of acceptable structural integrity (i.e. strength and form stability) which is most desirable since the pad forming process is generally an air-laid process.

It has been found desirable and advantageous to employ thermomechanical pulp in absorbent disposable structures due, not only to the obvious economic advantages but also due to improvements in absorbency. The later results from the semi-hydrophobic nature of thermomechanical pulp due to the presence of the natural lignins, which give greater resiliency to the non-woven pad and concomitant increased liquid holding capacity.

One of the disadvantages of thermomechanical pulp lies in the "off-colour" of the product which renders disposables made therefrom less desirable to the consumer, particularly those consumers using disposable diapers on babies where a very "white" product is considered a "must" or at least highly desirable.

It has now been found that the whiteness of thermomechanical pulp and other off-colour cellulosic pulps such as mechanical and even semi-chemical pulps and even chemical pulps which do not meet accepted standards of whiteness can be vastly improved in their whiteness, approaching the best of the chemical pulps (i.e. delignified and bleached) by treating the pulp, preferably in slurry form, with a mixed dye system comprising (a) Colour Index acid violet 49 and (b) Colour Index acid violet 47 in a weight ratio of (a) to (b) of from 10:1 to 1:10, preferably 6:1 to 1:6 and more preferably 4:1 to 1:4 and most preferably 3:1 to 1:3 and most preferably 1:1 to 1:3 to provide the pulp with from .001% to 0.05% weight of dye based on the dry pulp weight.

The dye mixture is conveniently added to the aqueous pulp (usually about 85 to 90% or more solids) as a solution preferably aqueous, but any suitable solvent for the dye (e.g. alcohol or alcohol/water) may be used. While the dye solution may be of any desirable concentration, it is generally preferred to use dilute solutions to obviate over-dyeing in localised portions of the pulp which may result due to rapid and fairly high exhaustion values of the dye from solution on to the ceilulosic material of the pulp.

After treatment, the pulp is handled in the conventional way to form sheet products for any subsequent use and in particular the pulp may be sheeted to form paperboard to be used in producing absorbent fluff for the disposable products mentioned above.

The invention may be put into practice in various ways and a number of specific embodiments will be described to illustrate the invention with reference to the accompanying examples.

EXAMPLE I To 1.5 g of an aqueous cellulose pulp (thermomechanical pulp - non-delignified) of 90% cellulosic solids there was added 50 cc of a dye solution containing (a) 7.5 milligrams/litre of Colour Index acid violet 47 and (b) 2.5 milligrams/litre of Colour Index acid violet 49. After drying the pulp, subsequent to screening to form a sheet, it was found that the Tappi brightness as conventionally measured on a G.E.

reflectometer was 80% whereas untreated pulp (i.e. without dye treatment sheeted similarly had a Tappi brightness of only 65%. The dye-treated product not only had improved brightness and whiteness, but was equivalent to the usual chemical pulp (delignified) when sheeted in a similar manner, notwithstanding the presence of the lignin in the thermomechanical material.

It may also be desirable to add a small amount of titanium dioxide or barium sulphate pigment to the aqueous pulp (furnish) to further whiten the product. Generally only very small quantities, from about 0.01% to about 10% by weight and preferably 0.5% to about 3% by weight are needed to yield outstanding results as illustrated in Examples IIA and IIB which follow.

EXAMPLES IIA and IIB Example IIA Example I is repeated with the addition to the dye solution of 0.5 g/litre of titanium dioxide.

Example IIB Example I is repeated with the addition to the dye solution of 0.5 g/litre of barium sulphate.

For each of the products of Example IIA and llB the brightness value of the product is 85%.

While the invention has been described with respect to a mixture of dyes CI 47 and CI 49, it is to be understood that other dyes of similar colour characteristics may be used. One of the significant characteristics of Cl 47 dye (.001% in water) is a prominent absorption in the visible region of from about 4800A to about 6000A with a flat peak at about 5100A to 5700A, and for the CI 49 dye (0.0005% in water) on broad absorption band in the region of about 4900A to about 6300A with a sharp double peak at about 5200A to about 61 ooh, and consequently other dyes of equivalent absorption characteristics may also be used.

Colour Index acid violet 49 is a triphenylmethane type dye (Colour Index No. 42640) and Colour Index acid violet 47 is an anthraquinone type.

Claims

1. A mixed dye composition for brightening and whitening cellulose material which comprises Colour Index dye 47 and Colour Index dye 49 in a weight ratio of from 10:1 to 1:10.

2. A mixed dye composition for brightening and whitening cellulose material which comprises a first dye having an absorption band from 4800A to 6000A and a second dye having an absorption band from 4900A to 6300A in a weight ratio of from 10:1 to 1:10.

3. A composition as claimed in Claim 1 in which the ratio is from 4:1 to 1 :4.

4. A mixed dye composition as claimed in Claim 1 substantially as specifically described herein with reference to the Examples.

5. A process for brightening and whitening aqueous cellulosic pulp which comprises adding thereto a solution of a dye composition as claimed in Claim 1 or Claim 2 or Claim 3.

6. A process as claimed in Claim 4 in which the solution is an aqueous solution.

7. A process as claimed in Claim 5 in which the dye composition in the solution ranges from 0.001% to 0.05% by weight.

8. A process as claimed in Claim 4, 5 or 6 which further includes the addition to the pulp of from 0.01% to 10% by weight of titanium dioxide or barium sulphate or mixtures thereof.

9. A process as claimed in Claim 4, 5, 6 or 7 in which the cellulosic material is derived from thermomechanical pulp.

10. A process for producing an absorbent product suitable for absorbing body fluids which comprises treating an aqueous cellulosic pulp with a composition as claimed in any one of Claiins 4 to 8, drying the treated pulp and thereafter forming an air-laid mass therefrom.

11. A process as claimed in Claim 4 substantially as specifically described herein with reference to the Examples.

12. An absorbent product suitable for absorbing body fluids comprising an air-laid cellulosic fluff treated with a dye composition as claimed in Claim 1 or Claim 2 or Claim 3.

13. An absorbent product as claimed in Claim 11 wherever made by a process as claimed in any one of Claims 4 to 10.

14. An absorbent product as claimed in Claim 12 in which the fluff is derived from thermomechanical pulp, the ratio of dye 49 to dye 47 ranges from 4:1 to 1:4 and the fluff contains from 0.001% to 0.05% by weight of the dye composition.

15. An absorbent product as claimed in Claim 12 in which the fluff is derived from thermomechanical pulp, the ratio of the first to second dye ranges from 4:1 to 1:4 and the fluff contains from 0.001 % to 0.05% by weight of the dye composition.

1 6. in a disposable product suitable for absorbing body fluids, a water impervious backsheet and a top sheet, the improvement wherein the absorbent mass comprises a product as claimed in Claim 11, 12or13.