EP0479146A2 - Use of propylene glycol monomethyl ether for dry cleaning - Google Patents

Abstract

Disclosed is a solvent for dry cleaning, comprising propylene glycol monomethyl ether and a solvent for dry cleaning, further containing water.

Description

BACKGROUND OF THE INVENTION
• This invention relates to a solvent suitable for dry cleaning.
• 1,1,1-Trichloroethane and perchloroethylene, which have been used in the prior art as solvents for dry cleaning , have the problem of polluting underground water, while some kinds of a fluorinated chloro carbon has the problem of destroying the ozone layer, and therefore there is currently a great need for rapid investigation of alternative substances.
• The present inventor has previously investigated the dry cleaning capabilities of 81 kinds of solvents (Journal of the Japan Research Association for textile End-use), 27, 8 (1986), 352 - 359), but there was no solvent which met all requirements.
• Solvent for dry cleaning must meet several requirements such as detergency, handleability, safety, etc.
• More specifically, detergency is measured according to "solubility" and "dispersibility" of various types of soil, including oil-soluble soils such as skin fat, fat and oil, oil mist, etc.; water-soluble soils such as sweat, water-soluble foods; dirts such as sludge, dust, etc., the degree of "counter-contamination", that is, soil washed from clothing migrating back from the cleaning liquid to the clothing, and the degree of small surface tension of the solvent penetrating into the clothing and between the soils. On the other hand, "handleability" is measured by easy drying of the article to be washed, long life, easy distillation and recovery of the solvent, suitability for machines with no corrosion of metals, easy workability and management with low odor, no remaining odor on the article to be washed, etc. "Safety" is measured by the degree of collapse of form of the article to be washed, denaturation of the article to be washed such as by yellow discoloration, run-off of dye, dissolution of auxiliary items such as buttons, high ignition point and flash point, low toxicity, etc.
• Propylene glycol monomethyl ether (hereinafter referred to as PM) has been known in the art as a solvent for home use (Japanese Unexamined Patent Publication No. 20400/1988), solvent for floor use (Japanese Unexamined Patent Publications Nos. 112699/1988 and 168498/1988), but not yet as a solvent for dry cleaning. The present inventor has found that PM is suitable as a solvent for dry cleaning from the standpoint of the various criteria mentioned above to accomplish the present invention.
SUMMARY OF THE INVENTION
• The present invention is a solvent for dry cleaning containing PM. The solvent for dry cleaning of the present invention may contain PM and water. In the case, water content is not more than 50 %, preferably, 0.4 % to 25 % with respect to the total volume of the solvent for dry cleaning. It is preferable that the water content is not more than 25 %, since the shrinkage of a weft of a cotton remains by 5 %.
  It will be seen from the various test results described below that PM has vast possibilities.
DETAILED DESCRIPTION OF THE INVENTIONTest example 1 (Solubility)
• Water, perchloroethylene, 1,1,1-trichloro-ethane, CFC 113 and PM were each employed as solvent, and distillation residue in cleaning factory was used as the oil-soluble soil, and instant coffee powder as the water-soluble soil solutes. The test was conducted by adding 5 ml of the above solvent to 0.5 g of the above solute in a test tube, leaving it to stand at 30 °C for 72 hours, and thereafter examining solubility with the naked eye.

  
• From Table 1, it can be seen that PM has both oil solubility and water solubility, and therefore is as effective on oil-soluble soils as the solvent of the prior art, and exhibits relatively better solubility for water-soluble soils, although inferior to water. In other words, while the chlorine type solvents of the prior art use soap to aid in dissolving performance for water-soluble soils, PM exhibited good detergency for water-soluble soils on its own. Also, PM has a surface tension of 27.7, which is greater than petroleum (18 - 19) and CFC-113 (17.3), and comparable to perchloroethylene (32.3) and 1,1,1-trichloroethane (25.6).
Test example 2 (Counter-contamination)
• A solvent with good counter-contamination is good in the finishing of dry cleaning, and can clean even with a liquid containing a great deal of contamination, and the number of distillations may be economically reduced.
• Counter-contamination is determined in consideration of the type of contamination (solute), the solvent and the kind of clothing, and therefore, the following test was carried out: as the water-soluble solute, soy sauce (0.5 ml) and coffee (0.5 g) were used; as the dispersible solute, carbon black (0.04 g) was used; as the oil-soluble solute, waste oil after prolonged usage of gear oil (2 g) was used and, as the miscible solute, distillation residue of cleaning (0.04g) was employed. The test was conducted by immersing and stirring a cloth strip of 2.5 x 2.5 cm in 75 ml of a solvent containing each solute dissolved therein, and soaking it for 5 minutes. After air drying, the reflectance of each cloth strip was measured by UV-200, and counter-contamination ratio was determined using the following formula.

  
• The results are shown in Table 2.

  
• From Table 2, the following facts can be seen.
• Soy sauce: Soy sauce is precipitated with a chlorine type solvent to float as a sol. The sol is hydrophilic, and therefore firmly adheres onto cotton, having a hydrophilic surface. It did not adhere to the wool, or polyester, which have hydrophobic surfaces. On the other hand, since the soy sauce was completely dissolved in water and PM, no dying, or counter-contamination was exhibited.
• Coffee: In a chlorine type solvent and PM, the solute floats as solid fine particles. The particles adhered selectively with perchloroethylene and CFC-113. They did not adhere with trichloroethane and PM. On the other hand, dyeability was great with water.
• Carbon black: This was not dissolved, but rather dispersed in all of the solvents, and there was no significant difference depending on the solvent.
• Waste oil: This was completely dissolved in a chlorine type solvent, without counter-contamination. On the other hand, in water and PM, the oil floated like a sol in the solution, and since the sol is lipophilic, it adhered onto the wool and polyester which have lipophilic surfaces.
• Distillation residue: This is a mixture of water-soluble, dispersible and oil-soluble, and further contains a soap for charge, and therefore may be considered to approximate the coditions of practical dry cleaning. In a chlorine type solvent, counter-contamination on wool, and cotton was marked, while the results with water were good. With PM, the results were between those of water and chlorine type solvents.
• From the results as described above, PM exhibits low counter-contamination for all kinds of contamination and clothing, and therefore can be evaluated as an exellent solvent for dry cleaning.
Test example 3 (shrinkability)
• A specific feature of dry cleaning is that water absorptive fibers are prevented from form collapsing or shrinkage of washed products by swelling resulting from water washing. Shrinkage of the clothing when washed with PM was tested.
• In a cup for laundermeter in which 10 steel balls and 100 ml of solvent were placed, test cloths with a thread mark of 10 x 10 cm attached at the center of the cloth strips of 12 cm x 12 cm of cotton, hemp, wool were added sheet by sheet, soaked at normal temperature for 45 minutes, then dried by flat drying, after which the length between the thread marks was measured. The results are shown in Table 3.

  
• As can be seen from Table 3, weft shrinkage was within 2%, but what is to be noted is that there was no great shrinkage at all even when water was added at 50%. This is due to the good hydratability of PM. In the case of 1,1,1-trichloroethane, perchloroethylene, when the water in the article to be washed mixes with the solvent, the water cannot be hydrated with the solvent and may cause the article to shrink, but PM will not give rise to such shrinkage, as shown in Table 3. However, it is preferred that the water content is not more than 25 % in order that the shrinkage to the any direction of the cotton does not exceeds 5 %.
Test example 4 (Combustibility)
• The flash point of PM is 36 to 38 °C, and readiness of combustion is approximately equal to that of petroleum solvents. However, the flash point of a mixture with 50% water is 62 to 64 °C, showing that elevation of the flash point can be effected by mixing with water.
Test example 5 (Readiness of drying)
• In the dry cleaning process, if a long time is required for the drying of the article to be washed, work efficiency will be markedly lowered. This test was conducted by piling 4 sheets of cotton cloths of 5 x 5 cm, adding by drops 0.125 g of each solvent, and measuring the vaporization rate of the solvent. The results compared the vaporization rates of the respective solvents with that of perchloroethylene (1) as shown in Table 4.Table 4

  	Perchloroethylene	1,1,1-trichloroethane	CFC-113	PM
  Using cotton cloth	1	3.929	14.643	0.386
  Solvent alone	1	4.444	13.667	0.244

• Although PM alone is slow to vaporize, the difference is not so great when accompanied with the article to be washed, such as cotton cloth. Slow vaporization rate in the case of solvent alone is desirable, because natural loss of the solvent during storage is small.
Test example 5 (Corrosiveness)
• A test strip 1 x 2 cm each of iron, aluminum, and stainless steel was dipped in the solvent at room temperature for one week and then taken out and left to stand in air for 3 months for judgement of the degree of oxidation. In PM, no change was observed at all for any of the test strips.
• The PM of the present invention has the following advantages as a solvent for dry cleaning:
• (1) It is effective for washing both oil-soluble and water-soluble contaminants.
• (2) Counter-contamination is little.
• (3) No soap is required.
• (4) The life of the solvent is long.
• (5) There is no corrosion of cleaning machine, etc.
• (6) Mixing with water is possible.

Claims (4)

1. A solvent for dry cleaning, comprising propylene glycol monomethyl ether.
2. The solvent of claim 1 wherein further contains water.
3. The solvent of claim 2 wherein the water content is not more than 50 % with respect to the total volume of the solvent.
4. The solvent of claim 3 wherein the water content is 0.4 % to 25 % with respect to the total volume of the solvent.