EP0368383A2

EP0368383A2 - Fabric conditioner

Info

Publication number: EP0368383A2
Application number: EP19890202705
Authority: EP
Inventors: Lisa Ann Dell'armo; Robert James Lala; John Edward Lovas; Oscar Walter Neiditch
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1988-11-09
Filing date: 1989-10-26
Publication date: 1990-05-16
Also published as: EP0368383A3; CA2002219A1

Abstract

Compositions and processes for coating a flexible subsstrate for subsequent use in a mechanical tumble clothes dryer are disclosed. The compositions incorporating fluorescent whitening agents impart improved whiteness to clothes treated in the dryer and the process provides a substantially safe and easy method for incorporating the fluorescent whitening agent into the coating composition.

Description

The instant invention relates generally to application of adjuvants to fabrics in tumbler-type automatic dryers, more particularly to articles, methods of preparation and methods of use for applying these adjuvants.
It has been customary for many years to include various adjuvants in detergents and rinse or wash-cycle additives. Fabric softeners and fluorescent whitening agents (FWA) which also have been called optical brighteners or fluorescent dyes are among the most common adjuvants used.
In the wash or rinse cycles, the primary objective is to remove soil, etc. from the cloth being washed by means of detergents, water and emulsifying agents. The presence of detergents and emulsifying agents effective to remove soil from the cloth manifestly renders difficult and less efficient the concurrent application of fabric softeners or other adjuvants to the same piece of material. Since the conditions characteristic of the rinsing and washing cycles, leading to inefficient application of the fabric adjuvants, are not present in the drying cycle, there is the potential for the much more efficient utilization and application of such adjuvants.
U.S. Patent 4,238,531 discloses the application of FWA and softeners, as well as many other adjuvants to fabrics in the dryer by use of a flexible substrate carrying the adjuvant. Some commercial dryer softener sheets also employ low amounts of FWA's, for example, 7-diethylamino-4-methylcoumarin (Aclarat 8678, a trademark for a product of Sandoz Chemical) at a level of about 0.1%.
Owing to the heat, mechanical action, and residual water on the fabrics in the dryer, it might be expected that fabric adjuvants could be easily and uniformly applied in the dryer. Experience demonstrates, however, that this does not readily occur and in the case of FWA's, it is particularly difficult.
Many patents over the last twenty or so years have dealt with various aspects of treating fabrics in the dryer or in both the washer and dryer, and these will be well known to the artisan. Fairly extensive listings of patents dealing with compositions, substrates and with methods of treating fabrics may be found in U.S. Patents 3,442,692; 3,895,128; 4,022,938; 4,085,052; 4,113,630; 4,177,151 and 4,199,465. Patents dealing with FWA's or optical brighteners and optical brighteners with fabrics are numerous. Several of these are U.S. 2,784,183 on monotriazoles and U.S. 2,612,501 concerned with triazines; U.S. 3,904,533 and 4,460,485 on liquid fabric conditioning agents incorporating brighteners and European Patent Application 0 006 271 dealing with washing and softening compositions containing a nonionic brightener. None of the art, however, has provided completely satisfactory whitening.
In its widest aspect, the invention provides a fabric conditioning article comprising a flexible sheet substrate which comprises a fabric conditioning composition which comprises at least 1 % by weight of a distyrylbiphenyl type of FWA in combination with a selected fabric softener or mixture of fabric softener and distributing agent. In some instances, selected carboxylic acids which have softening properties may be employed.
The inventive process for preparing said article provides a mixed solvent system balancing water and compatible hydroxylic solvents, such as glycols or glycerine, particularly glycerine, capable of substantially dissolving the optical brightener and solubilizing it to mix with the other components of the composition to facilitate coating of the substrate and distribution of the actives.

The fabric softening material

The fabric conditioning composition according to the present invention includes compounds generally classified as fabric softeners that are employed during the drying cycle of the home laundering operation. Such fabric softeners are preferably inorganic clays or water-soluble or water-dispersible organic, waxy materials having a preferred melting (or softening) point between about 25°C and 150°C. Softener materials of this type may also be fabric substantive in the sense that they are readily deposited on to the surfaces of fabrics treated therewith. Many fabric softeners of this type also impart some degree of static control to the fabrics being treated therewith.
The fabric softeners can be used singly or in admixture with one or more compatible fabric softeners. They can be selected from the following broadly denoted classes of compounds which preferably contain at least one long chain group:

(1) cationic quaternary ammonium salts including quaternary imidazolinium salts;
(2) nonionic compounds, such as sorbitan esters and ethyoxylated alcohols and alkylphenols;
(3) anionic soaps or free fatty acids, sulphates and sulphonates, e.g. fatty acid soaps, ethoxylated alcohol sulphates and sodium alkyl sulphates, alkyl sulphonates, sodium alkylbenzene sulphonates, and sodium or potassium alkylglyceryl ether sulphonates;
(4) zwitterionic or ampholytic tertiary or quaternary ammonium compounds such as for example tertiary amine oxides;
(5) tertiary ammonium compounds such as tertiary amines;
(6) smectite-type inorganic clays and

Preferred materials of type (1) are disclosed in EP 322 270. Preferably the fabric softener material is a cationic material which is relatively water-insoluble Highly preferred materials are cationic quaternary ammonium salts having two C12-24 hydrocarbyl chains, which are preferably ester-interrupted to provide biodegrability.
Well-known species of substantially water-insoluble quaternary ammonium compounds have the formula
wherein R₁ and R₂ represent hydrocarbyl groups from about 12 to about 24 carbon atoms; R₃ and R₄ represent hydrocarbyl groups containing from 1 to about 4 carbon atoms; and X is an anion, preferably selected from halide, methyl sulfate and ethyl sulfate radicals. Other preferred cationic compounds include those materials as disclosed in EP 239,910 (P&G), which is included herein by reference.
In this specification the expression hydrocarbyl group refers to alkyl or alkenyl groups optionally substituted or interrupted by functional groups such as -OH, -O-, -CONH, -COO-, etc.
Another class of preferred water-insoluble cationic materials are the hydrocarbylimidazolinium salts believed to have the formula:
wherein R₁₃ is a hydrocarbyl group containing from 1 to 4, preferably 1 or 2 carbon atoms, R₁₁ is a hydrocarbyl group containing from 8 to 25 carbon atoms, R₁₄ is an hydrocarbyl group containing from 8 to 25 carbon atoms and R₁₂ is hydrogen or an hydrocarbyl containing from 1 to 4 carbon atoms and A⁻ is an anion, preferably a halide, methosulfate or ethosulfate.
Preferred materials of type (2) are also disclosed in EP 322 270 and include glycerol esters, such as glycerol mono-stearate, fatty alcohols, such as stearyl alcohol, alkoxylated fatty alcohols C₉-C₂₄ fatty acids and lanolin and derivatives thereof.
Preferred materials of type (3) are soaps of free fatty acids thereof, such as for example disclosed in DE 29 43 606.
Preferred material of type (4) are disclosed in EP 322 270 and include amphoteric or zwitterionic tertiary or quaternary ammonium compounds having either one single very long hydrocarbyl side chain or two long hydrocarbyl chains. Amphoteric or zwitterionic ammonium compounds preferably have two long hydrocarbyl chains, each chain having 8-24 C-atoms, preferably 10-20 C-atoms, most preferred around 16 C-atoms.
Suitable amphoteric fabric substantive materials for use in a fabric treatment composition according to the invention are for instance hydrocarbyl betaines, hydrocarbylamido betaines, glycinates or propionates and tertiary amine oxides. The HLB of the amphoteric fabric substantive material is preferably less than 10.0.
Preferred materials of type (5) are amines as disclosed in EP 322 270. Preferred amines are tertiary amines comprising two long hydrocarbyl chains.
The level of fabric softening materials based on the total weight of the fabric conditioning composition on the substrate is preferably more than 5 %, more preferred more than 25 %, even more preferred more than 50 %, especially preferred more than 50 %, most preferred from 60% to 99%.

Distributing agents

Fabric conditioning compositions for use in laundry dryer products of the invention comprise one or more distributing agents. Any agent which facilitates the distribution of the softening materials on the fabrics under laundry dryer conditions, may be used. In some circumstances the distributing agent can be the same material as the softening material, for example long chain carboxylic acids generally act as softening ingredients and as distributing agent. In an extreme situation the fabric conditioning composition for use in the laundry dryer article according to the invention may therefore comprise only two ingredients, that is a softening ingredients which also acts as a distributing agents and a FWA. Preferably however fabric conditioning compositions for use in articles of the invention comprise at least three ingredients. one of these ingredients functioning as the main softening ingredient, the second ingredient functioning as the main distributing ingredients and possibly also as a co-softening ingredient, the third ingredient being the FWA. Preferably the main softening ingredient is a material of type (1), (4) or (5) as described above or mixtures thereof. Most preferably the main softening ingredient is of type (1) as described above. If softening materials of type (2) or (3) or mixtures thereof are used then they are preferably present as as co-softeners, which may also function as distributing agents.
Preferred distributing agents are disclosed in U.S. 4,238,531 and 4,327,133 which is herein incorporated by way of reference.
Suitable distributing agents for use in the present invention generally are innocuous substances, which, after formulation, are meltable, sublimable, soluble or softenable or otherwise spreadable at the temperatures encountered in the dryer. As a general rule, temperatures commonly encountered in home drying machines are in the order of from 75° to 200°F. It may be noted in this connection that a number of organic compounds are very effective distributing agents even though in the pure state they have melting points, softening points, etc., substantially above the temperatures encountered in drying machines. It will be understood, therefore, that when referring to the melting points or softening points relative to temperatures encountered in the drying machines, the melting point or softening point which controls the effectiveness of the spreading agent is the melting point or softening point of the formulated material containing both distributing agent and active ingredient rather than the melting point of the chemically pure substances.
Suitable materials which can be used as distributing agents in accordance with the present invention include, but are not limited to urea which is soluble in the entrained water accompanying the spun-dried clothing; ammonium carbonate which volatilizes at temperatures encountered in the drying machine; short chain quaternary compounds of the formula [N(R₂R₇R₈R₈)yX wherein R₂ is a C₁-C₄ alkyl, R₇ is a C₁₀-C₁₄ alkyl and each R₈ is either R₂ or R₇, X is an anion imparting water dispersibility and y is the valency of X, which generally are molten or softened at dryer temperatures; nonionic compounds such as ethoxylated fatty alcohols, which are molten or softened at dryer temperatures, and, moreover, because of their surface active characteristics, tend to promote spreading low molecular weight innocuous carboxylic acids such as citric acid, tartaric acid, gluconic acid, etc. which are soluble in the water accompanying spun-dried clothing and because of their acidity tend to promote solubilization and spreading of cationic fabric softeners.
Other distributing agents include, but are not limited to: phenyl stearyl trimethyl ammonium chloride, di(phenyl stearyl) dimethyl ammonium chloride, propylene glycol, silica gel and combinations of the above; ethoxylated amines such as those described in U.S. Pat. No. 2,979,528, fatty acids, Carbowax (polyethylene glycols), and block polymers of polyethylene glycol and polypropylene glycol such as described in U.S. Pat. Nos 2,674,619 and 2,677,700.
Especially preferred is the use of polyethylene glycol esters of carboxylic acids having a carbon chain lenght of from 5-30, more preferably from 8-22 and having a molecular weight of from 100 to 10,000, more preferably from 120- 5,000, most preferably from 150- 1,000. Especially preferred is the use of polyethylene glycol monostearate.
Other preferred distributing agents are or long-chain carboxylic acids preferably having a carbon chain lenght of from 5-30, more preferably from 8-22 such as commercial stearic acid and the like.
The amount of distributing agent is preferably at least 5% based on the weight of the fabric conditioning composition, more preferred more than 10 %, most preferred from 20 to 50 %. The amount of distributing agent should be sufficient to substantially facilitate distribution of the softener and FWA in use.

Fluorescent Whitening Agent

In addition to the fabric conditioning materials and distributing agents, a fluorescent whitening agent is required. The FWA of the invention is the distyrylbiphenyl compound of Formula I. Formula I is an ionic formula but it will be realized that the FWA is available as the sodium salt. Formula 1 is as follows:
The optical brightener must be present in an amount of at least 1% by weight of the fabric conditioning compositions on the substrate and not more than about 5%, preferably at least 1.3% and less than 4 %, most preferred from 1.3 to 3 %. This type of brightener, together with a softener on a foam dryer substrate, is disclosed in Example 1 of U.S. Patent 4,526,694. The brightener is also disclosed in an article by O.W. Neiditch in the Journal of the American Oil Chemists' Society, Vol. 58, No. 2, February 1981, pages 162 to 165A and in British Patent 2,028,365.

Preparation and Use of Impregnated Substrate Fabric Conditioning Articles

The fabric conditioning compositions are provided as a flexible sheet article of manufacture in combination with the fabric conditioning composition. Such articles can be designed for single usage or for multiple uses.
One such article comprises a flexible sheet material of sponge material releasably enclosing enough of the conditioning composition to effectively impart fabric softness and brightness during several drying cycles. In use, the composition melts and leaches out through the pores of the sponge to soften and brighten fabrics. Such a filled sponge can be used to treat several loads of fabrics in conventional dryers, and has the advantage that it can remain in the dryer after use and is not likely to be misplaced or lost.
A highly preferred article comprises the fabric conditioning compositions containing the softener, the distributing agent and the whitener releasably affixed to a sheet of paper or woven or non-woven cloth substrate. When such an article is placed in an automatic laundry dryer, the heat, moisture, distribution forces and tumbling action of the dryer remove the composition from the substrate and deposits it on to the fabrics.
The sheet conformation has several advantages. For example, effective amounts of the compositions for use in conventional dryers can be easily sorbed on to and into the sheet substrate by a simple dipping or padding process. Thus, the user need not measure the amount of the composition necessary to obtain fabric brightness. Additionally, the flat configuration of the sheet provides a large surface area which results in efficient release of the materials on to fabrics by the tumbling action of the dryer.
The water-insoluble paper, or woven or non-woven substrates used in the articles can have a dense or, more preferably, open or porous structure. Examples of suitable materials which can be used as substrates herein include paper, woven cloth, and non-woven cloth. The term "cloth" herein means a woven or non-woven substrate for the articles of manufacture, as distinguished from the term "fabric" which encompasses the clothing fabrics being dried in an automatic dryer. It is known that most substances are able to absorb a liquid substance to some degree; however, the term "absorbent", as used herein, is intended to mean a non-woven textile substrate with an absorbent capacity (i.e. a parameter representing a substrate's ability to take up and retain a liquid) from 1 to 25, more preferred from 4 to 12, most preferably 5 to 7, times its weight of water.
If the substrate is a foamed plastics material, the absorbent capacity is preferably in the range of 15 to 22, but some special foams, for example reticulated foams, can have an absorbent capacity in the range from 4 to 12.
Determination of absorbent capacity values is made by using the capacity testing procedures described in U.S. Federal Specifications (UU-T-595b), modified as follows:

1. tap water is used instead of distilled water;
2. the specimen is immersed for 30 seconds instead of 3 minutes;
3. draining time is 15 seconds instead of 1 minute; and
4. the specimen is immediately weighed on a torsion balance having a pan with turned-up edges. Absorbent capacity values are than calculated in accordance with the formula given in said Specification. Based on this test, one-ply, dense bleached paper (e.g., Kraft or bond having a basis weight of about 32 pounds per 3,000 square feet) has an absorbent capacity of 3.5 to 4; commercially available household one-ply toweling paper has a value of 5 to 6; and commercially available two-ply household toweling paper has a value of 7 to about 9.5.

Suitable materials which can be used as a substrate in the invention herein include, among other things, sponges, paper, and woven and non-woven cloth, all having the necessary absorbency requirements defined above.
The preferred non-woven cloth substrates can generally be defined as adhesively bonded fibrous or filamentous products having a web or carded fibre structure (where the fibre strength is suitable to allow carding), or comprising fibrous mats in which the fibres or filaments are distributed haphazardly or in random array (i.e. an array of fibres in a carded web wherein partial orientation of the fibres is frequently present, as well as a completely haphazard distributional orientation), or substantially aligned. The fibres or filaments can be natural (e.g. wool, silk, jute, hemp, cotton, linen, sisal, or ramie) or synthetic (e.g. rayon, cellulose ester, polyvinyl derivatives, polyolefins, polyamides, or polyesters).
The preferred absorbent properties are particularly easy to obtain with non-woven cloths and are provided merely by building up the thickness of the cloth, i.e. by superimposing a plurality of carded webs or mats to a thickness adequate to obtain the necessary absorbent properties, or by allowing a sufficient thickness of the fibres to deposit on to the screen. Any diameter or denier of the fibre (generally up to about 10 denier) can be used, inasmuch as it is the free space between each fibre that makes the thickness of the cloth directly related to the absorbent capacity of the cloth, and which, further, makes the non-woven cloth especially suitable for impregnation with a composition by means of intersectional or capillary action. Thus, any thickness necessary to obtain the required absorbent capacity can be used.
When the substrate for the composition is a non-woven cloth made from fibres deposited haphazardly or in random array on to the screen, the articles exhibit excellent strength in all directions and are not prone to tear or separate when used in the automatic clothes dryer.
Preferably, the non-woven cloth is water-laid or air-laid and is made from cellulosic fibres, particularly from regenerated cellulose or rayon. Such non-woven cloth can be lubricated with any standard textile lubricant. Preferably, the fibres are from 5 mm to 50 mm in length and are from 1.5 to 5 denier. Preferably, the fibres are at least partially oriented haphazardly, and are adhesively bonded together with a hydrophobic or substantially hydrophobic binder-resin, particularly with a nonionic self-cross-linking acrylic polymer or polymers. Preferably, the cloth comprises about 70% fibre and 30% binder-resin polymer by weight and has a basis weight of from about 18 to 45 g per square meter.
Preferbly the main surface of the flexible sheet article has a surface area of 1-2000 cm², more preferred from 5-500, most preferred from 20-300 cm². The thickness of the substrate is preferably less than 10 mm, more preferred less than 7 mm, especially preferred from 0.1 to 5 mm.
ln applying the composition to the absorbent substrate, the amount impregnated into and/or coated on to the absorbent substrate is conveniently in the weight ratio range of from about 10:1 to 0.5:1 based on the ratio of total fabric conditioning composition to dry, untreated substrate (fibre plus binder) in the final product. Preferably in the final product, the amount of the fabric conditioning composition ranges from about 5:1 to about 1:1, most preferably from about 3:1 to 1:1, by weight of the dry, untreated substrate.
Following application of the liquified composition, the articles are kept at room temperature until the composition substantially solidifies. The resulting dry articles, prepared at the composition substrate ratios set forth above, remain flexible; the sheet articles are suitable for packaging in rolls. The sheet articles can optionally be slitted or punched to provide a non-blocking aspect at any convenient time if desired during the manufacturing process.
The invention will be further illustrated by means of the following examples:
Fabric conditioner bases for use in the example comprise about 70% dimethyl, ditallow ammonium methyl sulphate (DTDMAMS), about 30% polyethylene glycol 200 monostearate (PEGS200 having a molecular weight of about 460) and varying amounts and types of FWA's.
Fatty carboxylic acids may be substituted for the polyethylene glycol monostearate. Examples of these carboxylic acids are commercial grades of stearic acid and the like which may contain small amounts of other acids.
The solvent system of preference is glycerine/water and preferably the optical brightener is dissolved in the glycerine/water to form a premix prior to addition to the softener base. The premix may also be propylene glycol or include propylene glycol but this is not preferred. The ratio of glycerine to water is about 4:1 but may vary between about two parts of glycerine to 1 part of water to six parts of glycerine to 1 part of water. The total amount of the solvent system is not critical and is usually about four to five per cent of the composition, but it may be less or more depending on solubility and final coating requirements.
After addition of the premix to the fabric conditioner base, the mixture is coated on a substrate in a known manner.
The composition of the invention is preferably prepared as follows:
A glycerin/water mixture (weight ratio about 4:1) is heated to about 180°F and then the FWA is added slowly with stirring. In the case of the FWA of Formula I, the colour of the premix solution is a bright yellow/green. The premix is added slowly to the softener base (which is preheated to 170-180°F). Once the premix is added and dissolved, perfume is added and mixed for several minutes.
Once the coating composition is prepared, the substrate is then coated by dipping or padding in a known manner.
The following Examples will more fully illustrate the embodiments of this invention. All parts, percentages and proportions referred to herein and in the appended claims are by weight unless otherwise indicated.

Example I

This example is an initial comparison of various fluorescent whitening agents added both with and without solubilization. The agent of the invention is shown above in Formula 1. Other fluorescent whitening agents (FWA) evaluated are listed in Table 1 along with their chemical type.

Table 1

Types of Fluorescent Whitening Agents
"F" Dye	Chemical Type
I	Distyrylbiphenyl
II	7 Diethylamino 4-methyl coumarin
III	Oxazole
IV	Morpholino disulphonated stilbene triazole
V	Phenyl stilbene triazole
VI	Methyl ethanolamine stilbene triazine disulphonate
VII	Diethanolamine disulphonated stilbene triazine

Each fluorescent whitening agent was dissolved in the fabric conditioner base comprising 70 % of DTDMAMS and 30 % of PEGS200 at a level of 1.3% for the initial evaluation. Several FWA's were difficult to dissolve, especially the agents of Formulas I, IV and VI. The FWA of Formula 11 was easy to dissolve even at the relatively high level of 1.3%.
The sheets were coated as follows:
A pre-weighed amount of a combination of 70% dimethyl ditallow ammonium methyl sulphate and 30% polyethylene glycol 200 monostearate was heated to about 160°F and slowly mixed. The FWA and the perfume were then added and stirred for varying amounts of time up to two hours for Formula I. The mixture was then transferred to a coater pan and the substrate sheets coated and dried, the weight ratio of fabric conditioning material to substrate in the final aricle is 2:1. The coated sheets were then evaluated in the dryer. Several fabric types were used for the evaluation - cotton, cotton terry, nylon, Dacron and Orlon. These fabrics were prewashed with an FWA-free detergent and a 3 pound ballast load and then dried in combination with the dryer sheets on the cotton/sturdy cycle for 30 minutes. Three pieces of each fabric were removed after the first dryer cycle. The remainder were re-washed and again treated with the dryer sheet a total of 4 times.

After the fabrics were washed, they were evaluated both visually and instrumentally for whitening potential. Instrumental "F" values were compiled for each fabric after 1 and 4 washes. The higher the "F" value, the greater the whitening potential. The results of initial screening Of the FWA'S are listed in Table 2.

Table 2

"F" Values of Fabrics After Treatment with Dryer Sheet Prototype
FWA	Formula	Cotton		Cotton Terry		Nylon		Dacron		Orlon
		1x	4x	1x	4x	1x	4x	1x	4x	1x	4x
No FWAs		5.4	5.4	5.4	5.5	4.9	5.0	5.4	5.3	5.7	5.8
1.3%	I	8.3	14.9	8.2	16.0	6.1	7.2	6.1	6.2	7.0	6.8
1.3%	II	6.1	7.0	-	-	5.2	5.7	5.3	5.4	5.9	6.0
1.3%	III	6.9	9.0	-	-	5.4	6.8	5.7	6.9	6.1	6.0
1.3%	IV	7.4	13.7	7.2	17.3	5.7	6.7	5.6	5.7	6.3	6.5
1.3%	V	7.6	12.7	8.3	14.1	6.0	8.3	5.9	6.3	6.5	6.9
1.3%	VI	7.5	13.7	7.1	16.3	5.7	6.4	5.9	6.4	6.4	7.1
1.3%	VII	6.9	13.8	7.7	15.4	6.1	6.4	5.5	5.7	6.4	6.6

Based on the above preliminary screening, 1.3% of Formula I appeared to be the best choice; the sheets made with Formula IV and Formula VI were not white when coated and the presence of the FWA produced a yellow sheet. Formulas VII and V gave slightly lower results on 100% cotton. Formula III was poor on cotton; its only advantage was a slight effect on Dacron after four (4) washes. Formula II was inferior to Formula I on all fabrics.

The next evaluation was to determine if the use of 1.3% of Formula I in a dryer sheet could be seen under realistic conditions of consumer usage. The same kind of fabrics were washed in the same manner as above but with a different commercial detergent and bleach and subsequently treated with either no sheet or a dryer sheet with 1.3% of Formula I. The instrumental results, which were also visually apparent, are listed in Table 3 below.

Table 3

"F" Values of Fabrics After Treatment with 1.3% of Formula I
	Cotton		Cotton Terry		Nylon		Dacron		Orlon
	1x	4x	1x	4x	1x	4x	1x	4x	1x	4x
Control	10.0	16.5	10.3	19.1	5.4	5.4	5.7	5.6	6.3	6.1
1.3% (Formula I)	10.0	18.1	10.5	20.7	6.9	7.5	6.3	6.7	6.9	7.2

Lower levels of the dye of Formula I were also evaluated. It was found that there was a small difference in "F" values between 1.3% Formula I and 0.75% Formula I. When both levels were evaluated vs. a commercial detergent wash with bleach, it was found that a level of 1.3% Formula I was needed to give a visual difference. These results are reported in Table 4.

Table 4

"F" Values of Fabrics After Treatment with Varying Levels of Formula I
	Cotton		Nylon		Dacron		Orlon
	1x	4x	1x	4x	1x	4x	1x	4x
Control	10.1	18.0	5.2	5.3	5.5	5.5	6.1	6.2
0.75% Formula I	10.4	19.1	6.1	5.7	5.9	5.9	6.6	6.6
1.3% Formula I	12.1	20.1	6.4	6.0	6.4	6.4	6.8	6.6

There was a slight difference between the control and 0.75% Formula I instrumentally, although visually the difference was hard to see. Formula I at 1.3% showed an improvement over the control.

It was desirable to improve the solubility of Formula I in the softener base. It was found that the compound of Formula I could be rendered more soluble by preparing a premix in propylene glycol and then adding it to the melted active. In this way FWA addition times in the laboratory were reduced from about 2 hrs. to less than five minutes via the inclusion of 4% propylene glycol in the fabric conditioning composition (basis active). Table 5 gives results of the evaluation of 0.75% Formula I with and without propylene glycol. These levels are also compared to 1.3% Formula I.

Table 5

"F" Values of Fabrics After Treatment with Dryer Sheets
	Cotton		Nylon		Dacron		Orlon
	1x	4x	1x	4x	1x	4x	1x	4x
1.3% Formula I	8.7	14.2	6.0	7.0	6.2	6.2	6.9	6.9
0.75% Formula I	7.7	11.8	5.8	6.7	6.0	5.7	7.1	6.7
0.75% Formula I + Propylene glycol	7.0	11.7	6.0	6.1	6.9	5.7	6.6	6.4

Although the propylene glycol solvent greatly aids solubility, it was still desirable to achieve solubility with a less volatile solvent.

Example II

A second series of experiments were run to attempt to improve the solubility of the fluorescent whitening agent of Formula I. Three separate formulations were prepared utilizing three separate procedures as follows:

1 2 3

Softener base 70% DTDMAMS, 30% PEGS200 95.7 91.7 90.72

Premix

Optical Brightener of Formula I 1.3 1.3 1.3

Glycerine - 4.0 4.0

Deionized Water - - 0.98

Perfume 3.0 3.0 3.0

100.0 100.0 100.0

Process parameters for the coating formulations were as follows:

Formulation #	1	2	3
Softener Base Temperature, °F
Heating	220	-	-
Cooling	175	-	-
Time, hours	8	-	-
Premix Temperature, °F	-	215-250	190
Final Coating Batch Temperature, °F	175	175	180

Viscosity, cps
Softener base	105	110	105
Softener base with Formula I (no perfume)	100	90	80
Final	85	70	55

The first test batch (Formulation 1) contained about 1800 pounds and required approximately 8 hours for heating, addition of the fluorescent whitening agent and cooling down to below 180°F for perfume addition. The coating formulation contained very fine particles of optical brightener and was translucent after 2 hours of mixing at 220°F. After then cooling the batch to 175°F, it was noted that discolouration and odour degradation of the softener base had occurred.
The glycerine/FWA premix solution presented several difficulties during processing of the Formulation 2 test batch. Initially the glycerine was heated to 210°F and the fluorescent dye was slowly added, however, after addition of approximately 50% of the required weight of FWA, the premix became a thick, lumpy viscous mass. The temperature of the glycerine was increased from 210°F to 245-250°F and addition of the FWA was resumed. Moderate-to-heavy smoking from glycerine vaporization was noted at the elevated temperatures. The final premix was a thick, lumpy, viscous slurry that will cause slurry transfer and handling problems.
The third test batch, Formulation 3, was the best of the three proposed methods for dispersion and dissolution of the fluorescent whitening agent. A small amount of deionized water (0.98% of the final formula) was added to the glycerine during the heating step. The mixture was heated to 190°F and the FWA was slowly added. The final premix was a low-viscosity, transparent, green fluorescent premix solution that was easily pourable into the softener base. Viscosity values of the softener base, the softener base with dye, and the final coating solution containing perfume were measured for each of the 3 test batches. These values were best for Formulation #3.
Each of the formulations were used to coat substrate sheets as described in example 1. A small quantity of these coated dryer sheets were then evaluated as follows:
A set of 4 coated dryer sheets from each test batch were selected and tested in the same manner as in Example I. The sheets contained similar coating weights to eliminate any bias from active and fluorescent dye concentrations on witening properties.

Several different types of test cloths, as listed, were selected and six samples of each were washed with a commercial detergent powder containing a fluorescent whitening agent together with a three-pound ballast load. The wash was bleached and then dried with one of the tes dryer sheets. Three of each of the test cloths were then evaluated (1x). The remaining three test cloths and ballast load were then washed, bleached and dried with a fresh test dryer sheet three more times and again evaluated (4x). The results were as follows:

Table 6

Average "F" Values of Fabrics After Treatment with Dryer Sheet Prepared by the Processes of Example 2
Treatment	Cotton		Nylon Taffeta		Spun Dacron		Orlon
	1x	4x	1x	4x	1x	4x	1x	4x
Control Commercial Dryer Sheet	18.6	25.9	5.7	5.8	5.4	5.4	6.0	6.3
Formulation 1	20.0	26.9	7.4	6.4	6.2	5.9	6.7	7.0
Formulation 2	19.3	26.8	6.3	7.1	6.0	6.2	6.8	7.3
Formulation 3	19.4	27.0	6.6	7.2	6.8	6.1	7.4	7.4

This evaluation shows the improvement in brightening over commercial sheets. The two formulations with 4% glycerine are directionally superior to the other one without glycerine but the third test batch (glycerine/water premix). delivered directionally better brightening than the other two batches. Visual evaluation agrees with the instrumental data.
This invention has been described with respect to certain preferred embodiments and various modifications thereof will occur to persons skilled in the art in the light of the instant specification and are to be included within the spirit and purview of this application and the scope of the appended claims.

Claims

1. A dryer sheet for treating damp fabric in a hot air tumbler fabric dryer during the drying cycle which comprises a fabric conditioning composition comprising:

a) an amount effective to soften said fabric of a fabric softening ingredient;

b) a distributing agent for said fabric softening ingredient; and

c) at least 1% by weight of said fabric conditioning composition of an alkali metal salt, preferably the sodium salt of a fluorescent whitening

said composition being carried on a flexible substrate.

2. A dryer sheet as defined in Claim 1 wherein said fabric softening ingredient is a cationic quaternary ammonium softener.

3. A dryer sheet as defined in Claim 2 wherein said distributing agent is selected from the group consisting of

(i) polyethylene glycol esters of fatty acids having a molecular weight of from 100 to 10,000,

(ii) soaps or free fatty acids; and mixtures thereof.

4. A dryer sheet as defined in Claim 1 wherein said fluorescent whitening agent is present in an amount of about 1.3% to 5% of said fabric conditioning composition.

5. A method for improved whitening of fabric comprising:
treating said fabric during the drying cycle in a hot air tumbler dryer while said fabric is damp by co-tumbling said damp fabric with a dryer sheet containing a fabric conditioning composition comprising

a) an amount effective to soften said fabric of a fabric softening ingredient;

b) a distributing agent for said fabric softening ingredient; and

c) at least 1% by weight of said fabric conditioning composition of an alkali metal salt, preferably the sodium salt of a fluorescent whitening agent of the formula (I) as described above said composition being carried on a flexible substrate.

6. A dryer sheet for treating damp fabric in a hot air tumbler fabric dryer during the drying cycle which comprises a fabric conditioning composition comprising:

a) an amount effective to soften said fabric of a fabric softening ingredient.

b) a distributing agent for said fabric softening ingredient; and

c) at least 1% by weight of said fabric conditioning composition of an alkali metal salt, preferably the sodium salt of a fluorescent whitening agent of the formula (I), said composition being carried on a flexible substrate, said composition having been applied to said substrate from a coating mixture prepared by adding a premix of said fluorescent whitening agent dissolved in a glycerine/water solvent mixture to a mixture of said softening ingredient and said distributing agent.

7. A method for preparing a dryer sheet containing a fabric conditioning composition comprising:
a) an amount effective to soften fabric of a fabric softening ingredient;
b) a distributing agent for said fabric softening ingredient; and
c) at least 1% by weight of said conditioning composition of an alkali metal salt, preferably the sodium salt of a fluorescent whitening agent of the formula I.
comprising:
heating said fabric softening ingredient; heating and adding said distributing agent to said fabric softening ingredient to form a softener base; mixing glycerine and water in a ratio of about two parts of glycerine to one part of water to six parts of glycerine to one part water; adding during mixing said fluorescent whitening agent to a sufficient amount of said glycerine water mixture to solubilize said agent and form a premix; adding said premix to said softener base to form a final coating solution; coating a substrate with said final coating solution and conditioning said coated substrate to form a dryer sheet.