IE50175B1

IE50175B1 - Disposable article of improved colour,composition and method for making same

Info

Publication number: IE50175B1
Application number: IE2321/80A
Authority: IE
Original assignee: Colgate Palmolive Co
Priority date: 1979-11-09
Filing date: 1980-11-07
Publication date: 1986-02-19
Also published as: AU6424780A; JPS5692964A; GR71714B; DE3041682A1; GB2068428B; ES496537A0; CH647799A5; BE886073A; IE802321L; BR8007216A; FR2486087A1; MX153471A; PT72011A; DK396680A; GB2068428A; PT72011B; ES8205553A1; CA1145508A; FR2486087B1; JPS6411668B2

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

The present invention relates to absorbent products which are generally characterised as disposable 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 Nos. 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. - 2 50175 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 nonwoven 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 verywhite 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 whitness 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 dye 49 and (b) Colour Index dye 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, preferably 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% by weight, 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 cellulosic material of the pulp. - 3 S0175 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 also extends to a disposable product suitable for absorbing body fluids comprising a water impervious back sheet and a top sheet and an absorbent mass located therebetween, the absorbent mass being a product in accordance with the present invention.

The invention may be put into practice in various ways and a number of 10 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% by weight cellulosic solids there was added 50 cc to a dye solution containing (a) 7.5 milligrams/1itre of Colour Index dye 47 (an acid violet dye) and (b) 2.5 milligram/1itre of Colour Index dye 49 (an acid violet dye). 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 20 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, nothwithstanding the presence of the lignin in the thermomechanical material.

It may also be desireable 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 - 4 5017S 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 IIB the brightness value of the product is 85%.

While the invention has been described with respect to a mixture of dyes Cl 47 and Cl 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% by weight in water) is a prominent absorption in the visible o o o region of from about 4800A to about 6000A with a flat peak at about 5100A to 5700A, and for the Cl 49 dye (0.0005.% by weight in water) on broad absorption O 0 band in the region of about 4900A to about 6300A with a sharp double peak o o at about 5200A to about 6100A, and consequently other dyes of equivalent 20 absorption characteristics may also be used. Colour Index acid violet 49 is a triphenylniethane type dye (Colour Index No. 42640) and Colour Index acid violet 47 is an anthraquinone type.

Claims

!. A mixed dye composition for brightening and whitening cellulose o material which comprises a first dye having an absorption band from 4800A o o o to 6000A and a second dye having an absorption band from 4900A to 6300A 5 in a weight ratio of from 10:1 to 1:10.
2. A mixed dye composition for brightening and whitening cellulose material which comprises as a first dye Colour Index dye 47 and as a second dye Colour Index dye 49 in a weight ratio of from 10:1 to 1:10.
3. A composition as claimed in Claim 1 or Claim 2 in which the ratio is 10 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 15 Claim 1, 2, 3 or 4.
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. 20
8. A process as claimed in Claim 5, 6 or 7 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 5, 6, 7 or 8 in which the cellulosic material is derived from thermomechanical pulp. - 6 50175
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 Claims 5 to 9, drying the treated pulp and thereafter forming an air-laid mass therefrom. 5
11. A process as claimed in Claim 10 in which the amount of dye used is such that the dried pulp contains from 0.001% to 0.05% by weight of the dye.
12. A process as claimed in Claim 5 substantially as specifically described herein with reference to the Examples.
13. An absorbent product suitable for absorbing body fluids comprising an 10 air-laid cellulosic fluff treated with a dye composition as claimed in Claim 1 or Claim 2 or Claim 3.
14. An absorbent product as claimed in Claim 13 whenever made by a process as claimed in any one of Claims 5 to 12.
15. An absorbent product as claimed in Claim 12 in which the fluff is 15 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.
16. In a disposable product suitable for absorbing body fluids, a water impervious backsheet and a top sheet, the improvement wherein the absorbent
17. 20 mass comprises a product as claimed in Claim 13, 14 or 15.