EMULSIONS OF EPOXY FUNCTIONAL SILICONE POLYETHERS
DESCRIPTION
Cross Reference to Related Applications
[0001] This application claims priority to US 60/631456, filed on November 29, 2004.
Technical Field
[0002] This invention relates to emulsions of epoxy functional silicone polyethers and their use in various softening applications such as tissue softening.
Background
[0003] Softness is a key product attribute in the production of tissue. Manufacturers of tissue utilize a variety of methods to improve the softness of their products; ranging from higher quality fibers, to adding debonders to the paper furnish, to utilizing new machine designs that minimize compression of the paper, to surface treatment of the tissue with organics and silicones.
[0004] Silicones can be used as surface treatments of tissue paper. For example, US Patent 5,059,282 teaches tissue paper having a soft, silky, flannel-like tactile feel through incorporation of an effective amount of a chemical additive such as a polysiloxane. Tissue paper embodiments of the '282 patent may further comprise a quantity of surfactant material to enhance softness and/or surface smoothness and/or wettability control; and/or a quantity of a binder material such as starch for linting control.
[0005] US Patent 4,950,545 teaches facial tissues containing a silicone compound exhibiting improved softness, and reduced lint while maintaining absorbency. The tissues of the '545 patent were taught not to smear glass, which occurs with many commercially available lotion-treated tissues.
[0006] There are long standing needs in tissue manufacture to continually improve the softness of tissue at low additive levels, while maintaining other key properties and parameters. In particular, manufacturers of tissue products seek a high level of softness of
the tissue while maintaining absorbency. Furthermore, the absorbency characteristics should be modifiable to meet the needs of different end-use applications.
[0007] The present inventors have discovered certain epoxy functional silicone polyethers are useful to enhance the softness of tissues while maintaining a high level of absorbency of the resulting tissue product.
Summary
[0008] This invention relates to emulsion compositions of an of epoxy functional silicone polyethers, and their use in various softening applications such as tissue softening. The present invention provides a method of treating a tissue comprising applying to the tissue an emulsion of an epoxy functional silicone polyether. The emulsion compositions of the present invention contain;
A) an epoxy functional silicone polyether, and
B) a surfactant.
Detailed Description
A ) The epoxy functional silicone polyether
[0009] The epoxy functional silicone polyether of the present invention is an organopolysiloxane comprising both an epoxy functional organic group and a polyether substituent. Organopolysiloxanes are known in the art and are typically represented as comprising M, D, T, and Q units, where "M" means a siloxane unit of formula R3SiOiZ2, "D" means a siloxane unit of formula R2Si02/2, "T" means a siloxane unit of formula RSiO3/2, where R is a monovalent organic group in any of these siloxane units, and "Q" means a siloxane unit of formula SiO4Z2. The M, D, T, and Q units may be bonded in various manners to form cyclic, linear, branched, or resinous structures. The molecular weights of the organopolysiloxane may vary.
[0010] The epoxy functional silicone polyether must comprise at least one epoxide functional organic group as a substituent. In other words, at least one of the R groups on the organopolysiloxane must be an epoxy functional organic group, herein denoted as R1. The epoxy can be any organic group containing a glycidyl ether group. The glycidyl ether may be attached to the organopolysiloxane via a divalent organic group, typically a divalent
hydrocarbon containing 2 to 12 carbon atoms, such as propylene (-CH2CH2CH2-), butylene, hexylene, and the like. Alternatively, R1 is propyl glycidyl ether. [0011] The quantity of the epoxide functional group substituent present on the organopolysiloxane can be expressed as the mole percent of the siloxy units containing such epoxide functionality, which typically ranges from 0.1 % to 20 %, or alternatively, from 0.5% to 5%.
[0012] The epoxy functional silicone polyether must comprise at least one polyether substituent in its molecule. In other words, at least one of the R groups of the organopolysiloxane as described above must be a polyether, denoted as R2. As used herein, "polyether" denotes a polyoxyalkylene copolymer unit represented by the formula - (CmH2mO)- wherein m is from 2 to 4 inclusive. The polyoxyalkylene copolymer unit typically can comprise oxyethylene units -(C2H4O)- , oxypropylene units -(C3H6O)-, oxybutylene units -(C4H8O)-, or mixtures thereof. The oxyalkylene units can be arranged in any fashion to form either a block or randomized copolymer structure, but preferably form a randomized copolymer group. Typically, the polyoxyalkylene block comprises both oxyethylene units (C2H4O) and oxypropylene units (C3H6O) in a randomized copolymer, as represented by the average formula -(C2H4O)a(C3H6O)b- , where a can range from 0 to 40, alternatively from 10 to 30, or alternatively from 20 to 30; and b can range from 0 to 40, alternatively from 10 to 30, or alternatively from 20 to 30. The polyoxyalkylene copolymer may be bonded to the organopolysiloxane via a divalent hydrocarbon group, which is typically a propylene group, -CH2CH2CH2-, or isobutylene group. The polyoxyalkylene copolymer unit may be terminated by a hydrogen atom (i.e. the terminal oxyalkylene unit has a hydroxyl group at one end), an organic ester such as an acetoxy group, or a monovalent alkyl such as a methyl group. [0013] The quantity of the polyether functional group substituent present on the organopolysiloxane can be expressed as the mole percent of the siloxy units containing such polyether groups, which typically ranges from 1 to 40%, or alternatively, from 5 to 20 %. [0014] The polyether and epoxide group may be substituents on any siloxy units in an organopolysiloxane terpolymer. Alternatively, both the polyether and epoxide groups may be substituents on independent disiloxy units in a "rake-type" organopolysiloxane terpolymer structure.
[0015] Organopolysiloxane terpolymers useful as epoxy functional silicone polyethers in the present invention may be represented by the formula (I):
R3SiO[R2SiO]x [RR1SiOIy [RR2SiO]2 SiR3 where: x can range from 1 to 1000, alternatively from 50 to 200, or alternatively from 100 to 150; y can range from 1 to 100, alternatively from 1 to 20, or alternatively from 1 to 5; z can range from 1 to 200, alternatively from 5 to 50, or alternatively from 5 to 15; R is a monovalent organic group, alternatively R is an alkyl group containing 1 - 30 carbons, alternatively R is methyl; R1 is an epoxy functional organic group, alternatively R1 is a glycidyl ether functional organic group, alternatively R1 is propyl glycidyl ether; R2 is a polyether functional organic group, alternatively is a polyether functional organic group containing oxyethylene units - (C2H4O)- , oxypropylene units -(C3H6O)-, oxybutylene units -(C4H8O)-, or mixtures thereof, alternatively R2 is a polyether functional organic group containing oxyethylene units (C2H4O) and oxypropylene units (C3H6O) in a randomized copolymer, as represented by the average formula -(C2H4O)a(C3H6O)b- , where a can range from 0 to 40, alternatively from 10 to 30, or alternatively from 20 to 30; and b can range from 0 to 40, alternatively from 10 to 30, or alternatively from 20 to 30.
[0016] Non-limiting examples of organopolysiloxane terpolymers useful as epoxy functional silicone polyethers can be represented by the following formula (II);
Formula II
CH3-[-P0]a[E0]b
where x can range from 1 to 1000, alternatively from 50 to 200, or alternatively from 100 to 150; y can range from 1 to 100, alternatively from 1 to 20, or alternatively from 1 to 5; z can range from 1 to 200, alternatively from 5 to 50, or alternatively from 5 to 15; PO is an oxypropylene unit, EO is an oxyethylene unit; a can range from 0 to 40, alternatively from 10 to 30, or alternatively from 20 to 30; and b can range from 0 to 40, alternatively from 10 to 30, or alternatively from 20 to 30. In the above structure, the polyether substituent as represented by -[PO]a[EO]t>- can be either a block copolymer or a randomized copolymer, but preferably the EO and PO units are a randomized copolymer. [0017] The epoxy functional silicone polyethers can be prepared by techniques known in the art, and many are commercially available. Typically, the epoxy functional silicone polyether is prepared by the platinum catalyzed hydrosilylation reaction of a SiH containing organopolysiloxane, such as MDxD(y+Z)HM (where DH represents the RSiHO2/2 siloxane unit, and x, y, and z are as described above) with both an alkenyl terminated polyoxyalkylene copolymer and alkenyl terminated organic group containing an epoxy group. The hydrosilylation can proceed in a simultaneous manner, that is where both the alkenyl terminated polyoxyalkylene copolymer and alkenyl terminated organic group containing an epoxy group are added together with the SiH containing organopolysiloxane, or in a stepwise manner, where one is added before the other.
(B) The Surfactant
The surfactant can be any cationic, anionic, non-ionic, or zwitterionic surfactant known in the art to stabilize emulsions of organopolysiloxanes. Typically, the surfactant is a non-ionic surfactant. Useful nonionic surfactants may be exemplified, but not limited to, polyoxyalkylene alkyl ethers, polyoxyalkylene sorbitan esters, polyoxyalkylene alkyl esters, polyoxyalkylene alkylphenyl ethers, ethoxylated amides, ethoxylated amines, ethoxylated siloxanes, polyvinylacetate hydrolysate, polyvinylalchohol, polyglycerols, and block copolymers of propylene oxide and ethylene oxide and others, and mixtures thereof. When nonionic surfactants are used in the present invention, polyoxyalkylene alkyl ethers or secondary alcohol ethoxylates are preferred. Representative examples of commercial polyoxyalkylene alkyl ethers, include Brij 30® , Brij 35L®, and Brij 97® produced by Uniqema (ICI Surfactants, Wilmington, DE) and mixtures thereof. Representative examples of commercial secondary alcohol ethoxylates include the Tergitol® surfactants (Dow Chemical, Midland, MI) such as Tergitol® 15-S-l 5.
[0018] Since emulsions are susceptible to microbiological contamination, a preservative may be used as an optional component of the emulsion, and some representative compounds which can be used include formaldehyde, salicylic acid, phenoxyethanol, DMDM hydantoin (l,3-dimethylol-5,5-dimethyl hydantoin), 5-bromo-5-nitro-l,3-dioxane, methyl paraben, propyl paraben, sorbic acid, imidazolidinyl urea sold under the name
GERMALL® II by Sutton Laboratories, Chatham, New Jersey, sodium benzoate, 5-chloro-2- methyl-4-isothiazolin-3-one sold under the name KATHON CG by Rohm & Haas Company, Philadelphia, Pennsylvania, and iodopropynl butyl carbamate sold under the name GLYCACIL® L by Lonza Incorporated, Fair Lawn, New Jersey. [0019] A freeze/thaw stabilizer can be included as an optional component of the emulsion including compounds such as ethylene glycol, propylene glycol, glycerol, trimethylene glycol.
[0020] Another optional component is a corrosion inhibitor such as an alkanolamine, an inorganic phosphate such as zinc dithiophosphate, an inorganic phosphonate, an inorganic nitrite such as sodium nitrite, a silicate, a siliconate, an alkyl phosphate amine, a succinic anhydride such as dodecenyl succinic anhydride, an amine succinate, or an alkaline earth sulfonate such as sodium sulfonate or calcium sulfonate.
[0021] The amounts of components (A) and (B) in the aqueous emulsion can vary but typically range as follows;
(A) 1 to 50 wt. %, alternatively 10 to 40 wt %, or alternatively from 20 to 30 wt%,
(B) 0.1 to 20 wt. %, alternatively 1 to 10 wt %, or alternatively from 1 to 5 wt%, where the remainder of the emulsion composition (that is so all components add to 100 weight percent) is water and/or additional additives as described above. [0022] Preparation of the emulsion involves mixing water, one or more surfactants, optional additives, and the epoxy functional silicone polyether, and homogenizing the mixture using a laboratory homogenizer or other device for applying vigorous agitation. Such compositions can generally be prepared at room temperature using simple propeller mixers, turbine-type mixers, Brookfϊeld counter-rotating mixers, or homogenizing mixers. No special equipment or processing conditions are generally required.
[0023] A representative emulsion of an epoxy functional silicone polyether useful in the present invention is Dow Corning® TM 4060 Emulsion (Dow Corning Corporation, Midland, MI).
[0024] The epoxy functional silicone polyether can be applied to a tissue paper as it is being made on a papermaking machine or thereafter, either while it is wet or dry. Examples and further description of application techniques are taught in U.S. Patent Nos. 4, 950,545, and 5,059,282, which are incorporated herein by reference. Typically, an aqueous mixture containing the epoxy functional silicone polyether is sprayed onto the tissue as it comes through the papermaking machine. While any amount of the epoxy functional silicone polyether emulsion may be applied, typically sufficient amounts are used to provide a dry coating having 0.1 to 6, alternatively 0.1 to 4, or alternatively from 0.25 to 2 weight percent of the epoxy functional silicone polyether on the tissue paper.
Examples
[0025] These examples are intended to illustrate the invention to one of ordinary skill in the art and should not be interpreted as limiting the scope of the invention.
Example 1
A representative emulsion of an epoxy functional silicone polyether was evaluated for its softening and absorbency vs other conventional silicone emulsions as coating treatments on tissue. The following emulsions were used as provided;
Emulsion 1 - Dow Corning® TM 4060 Emulsion (Dow Corning Corporation, Midland, MI), a nonionic emulsion containing 20 weight percent of an epoxy functional silicone polyether having a structure conforming to Formula II as described above.
Emulsion IA - Dow Corning® TM 4010 Emulsion (Dow Corning Corporation, Midland, MI), a nonionic emulsion containing 30 weight percent of a polydimethylsiloxane fluid having a viscosity of 350 mm2/s at 23°C, and emulsified with 10 wt % of a silicone polyether having similar structure conforming to Formula II as described above, except containing no epoxy functional groups.
Emulsion IB - is Dow Corning® TM 4050 Emulsion (Dow Corning Corporation, Midland, MI), a nonionic emulsion containing 18 weight percent of an amide functional organopolysiloxane. This emulsion was used as a representative silicone emulsion used in the textile industry for fabric softening.
Emulsion 1C - is Dow Corning® TM 401 1 Emulsion (Dow Corning Corporation, Midland, MI), an emulsion containing 30 weight percent of a polydimethylsiloxane fluid having a viscosity of 350 mm2/s at 23°C, emulsified with a polyoxyalkylene alkyl ethers.
Emulsion ID - Dow Corning® TM 4012 Emulsion (Dow Corning Corporation, Midland, MI), a nonionic emulsion containing 30 weight percent of a silicone polyether having a structure similar to Formula II as described above, except containing no epoxy functional groups.
[0026] These emulsions were applied to tissue by off-set gravure roll with the add-on to be 1 weight percent of the tissue basis weight. The coating was applied to one side of the tissue. The tissue was an embossed 4-ply with a basis weight of 61 grams per square meter. [0027] The treated tissue samples were then evaluated for relative Hand. Samples, identified with three digit codes, were presented to panelists in random order. Panelists were asked to rank the samples in order of least soft to most soft. Ranking data were averaged to give the highest softness rank where the highest value is 4.0 and the lowest is 1.0. [0028] The treated tissue samples were also evaluated for their absorbency abilities using an aged absorbency test. The tissue sample rolls were stored @ 50C & 0% Relative Humidity in a folded, not sealed polyethylene storage bag. After 14 days Absorbency Time (seconds) for 100% saturation of 1 sheet of tissue (4-ply sheet 22.6 x 13.6 cm with basis weight of 61 grams per square centimeter) was tested. The samples were folded three times to form a 5.7 cm x 6.8 cm sample then stapled on four corners. The samples were individually dropped into a one liter bowl of deionized water. The samples were dropped from a height of 1 to 3 cm above the water. The timer was started once the samples were released. The timer was stopped once 100% of the tissue had changed to a hue of gray due to water absorption. [0029] The results are summarized in the following table.
***** = Highest degree of softness per panel test.
2***** = Highest degree of absorbency - 100% sample saturation after 14-day storage at 5O
0C and 0% relative humidity.
These results show the emulsion of the epoxy functional silicone polyether had the best combination of softening (relative hand) and absorbency when compared to other silicone emulsions.