SOLUBLE LAUNDRY SHEET COMPRISING POLYOL OR METAL ION CHLORIDE

Abstract

The present invention provides a water-soluble laundry sheet comprising a detergent ingredient for laundry, a water-soluble film-forming polymer, and an alkali binder, wherein the laundry sheet comprises any one or more selected from the group consisting of polyols and metal ion chlorides. The present invention provides a water-soluble laundry sheet with enhanced formulation stability, storage stability, and sheet solubility.

Claims

1. A water-soluble laundry sheet comprising a laundry detergent ingredient, a water-soluble film-forming polymer and an alkali builder, wherein the water-soluble laundry sheet comprises at least one selected from the group consisting of a polyol and metal ion chloride.

2. The water-soluble laundry sheet according to claim 1, wherein the detergent ingredient is a C8-C18 alkyl sulfate alkali metal salt.

3. The water-soluble laundry sheet according to claim 2, wherein the detergent ingredient comprises at least one selected from the group consisting of a-olefin sulfonates, sodium lauryl sulfate, sodium lauryl ethoxylated sulfonate, secondary alkane sulfonates and methyl ester sulfonate.

4. The water-soluble laundry sheet according to claim 1, wherein the water-soluble film-forming polymer comprises polyvinyl alcohol or a polyvinyl alcohol-based copolymer.

5. The water-soluble laundry sheet according to claim 4, wherein the polyvinyl alcohol or polyvinyl alcohol-based copolymer has a number average molecular weight of 10,000-100,000 and a saponification degree of 65-95%.

6. The water-soluble laundry sheet according to claim 1, wherein the water-soluble film-forming polymer is used in an amount of 18-38 wt % based on the total weight of the water-soluble laundry sheet after drying.

7. The water-soluble laundry sheet according to claim 1, wherein the detergent ingredient is used in an amount of 30-60 wt % based on the weight of the water-soluble laundry sheet after drying.

8. The water-soluble laundry sheet according to claim 1, wherein the alkali builder is at least one selected from the group consisting of sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, sodium metasilicate, alkaline sodium silicate, neutral sodium silicate, sodium tripolyphosphate, sodium pyrophosphate, sodium borate, sodium aluminosilicate, sodium sesquicarbonate, monoethanolamine (MEA) and triethanolamine (TEA).

9. The water-soluble laundry sheet according to claim 1, wherein the polyol is at least one selected from the group consisting of erythritol, xylitol, mannitol, arabitol and sorbitol.

10. The water-soluble laundry sheet according to claim 1, wherein the polyol is comprised in an amount of 5-20 wt % based on the total weight of the dried water-soluble laundry sheet.

11. The water-soluble laundry sheet according to claim 1, wherein the metal ion chloride comprises at least one selected from the group consisting of sodium chloride, magnesium chloride, calcium chloride and potassium chloride.

12. The water-soluble laundry sheet according to claim 11, wherein the metal ion chloride is sodium chloride.

13. The water-soluble laundry sheet according to claim 11, wherein the chloride is comprised in an amount of 1-10 wt % based on the total weight of the water-soluble laundry sheet after drying.

14. The water-soluble laundry sheet according to claim 13, wherein the chloride is used in an amount of 3-7 wt % based on the total weight of the water-soluble laundry sheet after drying. 15

15. The water-soluble laundry sheet according to claim 1, which has a tensile strength of 0.79-3.8 kgf/cm.sup.2 as determined by the test instrument of 500 N zwicki, Zwick Roell, at 25° C.

16. The water-soluble laundry sheet according to claim 1, wherein said at least one selected from the group consisting of a polyol and metal ion chloride is a polyol.

17. The water-soluble laundry sheet according to claim 1, wherein said at least one selected from the group consisting of a polyol and metal ion chloride is a metal ion chloride.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0057] FIG. 1 and FIG. 2 illustrate a method for evaluating the formulation of a soluble sheet. FIG. 1 shows a sheet attached to a release sheet after drying, and FIG. 2 shows a sheet broken upon the detachment from the release sheet after drying. FIG. 1 shows an embodiment illustrating whether the sheet attached to the release sheet can be detached therefrom or not. FIG. 2 shows an embodiment illustrating whether the sheet is broken or not upon the detachment from the release sheet after drying.

[0058] FIG. 3a illustrates the result of evaluation of stability of a soluble sheet with time. Portion (b) shows a change in content of soda ash right after the preparation, when adding no sorbitol, and portion (a) shows a change in content of soda ash after storing the sheet at room temperature for 4 weeks. After the lapse of 4 weeks, there is a difference in content (Comparative Example 1). FIG. 3b illustrates whether the storage stability of the water-soluble sheet obtained according to Example 8 is improved or not. As determined from the results right after the preparation (b) and after storing the sheet at room temperature for 4 weeks (a), addition of sorbitol can prevent decomposition of soda ash (sodium carbonate). FIG. 3c illustrates the result of improvement of the stability of a sheet depending on the content of sorbitol. The two arrow marks show the peaks of soda ash. Addition of sorbitol prevents decomposition of soda ash, which suggests that the sheet detergent has reinforced heat stability.

[0059] FIG. 4 illustrates the result of comparison of cleaning power depending on the presence of sorbitol. The sheet not including sorbitol shows significant degradation of cleaning power after 4 weeks. In other words, FIG. 4 illustrates the result of comparison of storage stability with time for 4 weeks.

[0060] FIG. 5 illustrates the test result of the solubility of a sheet including sorbitol.

[0061] FIG. 6 shows the result of evaluation of cleaning power of a soluble sheet, and illustrates Comparative Example 1, Example 8, Example 9 and Example 10, when viewed from the left side.

[0062] FIG. 7 illustrates IR peaks of a blend for preparing a sheet including sodium chloride (salt) and a sheet not including salt. Portion (a) shows the result of a salt-free blend, and portion (b) shows the result of a blend including 5% of salt. The peak intensity of a laundry active ingredient varies depending on the presence of salt.

[0063] FIG. 8a illustrates the result of comparison of the storage stability of a sheet with time for 4 weeks, depending on salt content. When salt is used at 5 wt %, the sheet shows higher storage stability. In FIG. 8b, blue colored graph (c) shows the initial value, and red colored graph (d) shows the value after the lapse of 4 weeks. As the content of salt is increased, the difference between the blue colored graph and the red colored graph is reduced, wherein a smaller difference between the two graphs suggests improvement of stability.

[0064] FIG. 9 illustrates the result of evaluation of the solubility of a sheet including salt (bottom, Example 13) and that of a sheet not including salt (top, Comparative Example 9). The sheet including salt, shown at the top, shows higher solubility.

[0065] The longitudinal axis in each IR graph shows transmittance (%) and the transverse axis thereof shows a wave number (cm.sup.−1).

MODE FOR INVENTION

[0066] Examples will be described more fully hereinafter so that the present disclosure can be understood with ease. The following examples may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth therein. Rather, these exemplary embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. As used herein, temperature refers to a Celsius temperature (° C.), unless otherwise stated. In the following examples, PVA is JR-05 available from JAPAN VAM & POVAL CO., LTD. The PVA has a saponification degree of 72% and a polymerization degree of 500. The other ingredients are commercially available produces and purchased from the production companies.

1. Manufacture of Soluble Sheet Including Polyol

Manufacture of Soluble Sheet Including Sorbitol

[0067] First, a blend was prepared by introducing a formulating agent as a water-soluble film-forming polymer, a polyol, a detergent ingredient, a laundry aid and other ingredients, in turn, to water at 60° C., wherein agitation was carried out at 180 rpm until the introduced ingredients were dissolved completely in each introduction step. Herein, the amount of water was the same as the combined weight of the formulation agent+polyol+detergent ingredient+laundry aid+other agents (50% aqueous solution was prepared).

[0068] In the formulation process, the blend was formed into a sheet having a size of 15×25 cm and a thickness of 1.5 mm with a doctor blade, and then the sheet was dried in a drying oven at 125° C. for 12 minutes.

Evaluation of Formulation of Water-Soluble Laundry Sheet

[0069] The following test was carried out.

[0070] After each sheet is prepared, it is observed whether the phenomena as shown in FIG. 1 and FIG. 2 occur or not. In other words, each sheet is observed whether or not it is attached to the release sheet after the manufacture to prevent its separation from the release sheet, and then whether or not each sheet is broken upon the detachment from the release sheet.

[0071] The test was carried out in a constant-temperature/constant-humidity chamber under the condition of 20° C. and 30%. Each sheet is manufactured five times repeatedly.

[0072] When all of the phenomena are not observed, the sheet is evaluated as ‘good’. When the phenomenon as shown in FIG. 1 is observed, the sheet is evaluated as ‘poor’. In addition, both of the phenomena as shown in FIG. 1 and FIG. 2 are observed, the sheet is evaluated as ‘very poor’.

[0073] As can be seen from the following test result, a laundry sheet can be formulated even when adding a polyol instead of a formulating agent.

Evaluation of Stability with Time through IR

[0074] A water-soluble laundry sheet made by using PVA is problematic in that decomposition of a detergent ingredient and laundry aid is accelerated with time due to the decomposition of PVA. Thus, it is determined whether addition of a polyol improves storage stability or not.

[0075] The blend for a laundry sheet having the following composition and prepared as 50% aqueous solution was analyzed by IR spectrometry.

[0076] Right after manufacturing the sheet, IR was measured. Then, IR was further measured after storing (20° C., 30%, stored in a package made of PET 16+LLDPE55) the sheet for 4 weeks (test instrument: Perkin Elmer ultra two, constant-temperature/constant-humidity chamber, temperature 20° C., humidity 30%).

[0077] In the spectrum, variations at 1410 and 1450 cm.sup.−1 were observed. The peaks correspond to CO.sub.3.sup.2+ in Na.sub.2CO.sub.3. When the reaction of Na.sub.2CO.sub.3+H.sub.2O->2NaOH+CO.sub.2 proceeds due to the heat and water that are in contact with Na.sub.2CO.sub.3 during the storage, CO.sub.3.sup.2− is consumed. Therefore, it is thought that the intensity at 1410 and 1450 cm.sup.−1 is reduced in this case.

[0078] When sorbitol is present, it is possible to delay such reduction of Na.sub.2CO.sub.3 as an alkali builder.

[0079] It can be seen from the above result that the laundry sheet shows highly improved cleaning power.

Soluble Sheet Having Improved Quality by Using Polyol (Sorbitol)

[0080] The laundry sheets having the following compositions were manufactured and evaluated.

TABLE-US-00001 TABLE 1 Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Formulating 40 37 35 30 25 23 20 17 15 10 agent (PVA) Sorbitol — 3 5 10 15 17 20 23 25 30 Detergent 50 50 50 50 50 50 50 50 50 50 ingredient (SLS) Builder 7 7 7 7 7 7 7 7 7 7 (Na.sub.2CO.sub.3) Enzyme 2 2 2 2 2 2 2 2 2 2 Others 1 1 1 1 1 1 1 1 1 1 (fragrance, etc.) Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Formulation Good Good Good Good Good Good Good Good Poor Poor Mass Good Good Good Good Good Good Poor Very Very Very productivity Poor Poor Poor Storage Fair Fair Good Very Very Very Very Very Very — stability Good Good Good Good Good Good Dissolution rate Fair Poor Good Good Very Very Very Very Very — Good Good Good Good Good

[0081] As shown in the following Table 2, various types of polyols were used to carry out the test.

TABLE-US-00002 TABLE 2 Ex. 5 Ex. 6 Ex. 7 Formulating agent 25 25 25 (PVA) Polyol 15 15 15 Detergent ingredient 50 50 50 (SLS) Builder (Na.sub.2CO.sub.3) 7 7 7 Enzyme 2 2 2 Others (fragrance, 1 1 1 etc.) Total 100.0 100.0 100.0 Formulation Good Good Good Remarks Erythritol Xylitol Sorbitol is used is used is used

[0082] It is shown that the sheets obtained by using each of sorbitol, erythritol and xylitol as a polyol can be formulated with ease and shows an effect similar to the effect of sorbitol.

[0083] When using a polyol, it is easy to formulate a sheet, even when the content of the formulating agent in the sheet is reduced to at most 23% based on the total weight of the sheet.

[0084] It is also shown that when the content of sorbitol is less than at most 20 wt % and the tensile strength is 0.79-3.87 kgf/cm.sup.2, the sheet mass productivity is excellent. In addition, when the content of sorbitol is 10-20 wt % based on the total weight of the sheet, the solubility is improved.

Evaluation Result 3 Change in Cleaning Power Depending on Sheet Storage Period (Sorbitol Used Vs. No Sorbitol Used) (Storage Condition 20° C., Humidity 30%)

[0085] The cleaning power of the sheet according to Comparative Example 1 was compared with that of the sheet according to Example 3, right after the manufacture of each sheet and after storing each sheet for 4 weeks. The result is shown in FIG. 4.

[0086] The cleaning power was evaluated by the following method.

[0087] 1. Terg-o-tometer, water IL, water temperature 20° C., hardness 50 ppm

[0088] 2. Used contaminated cloth: Japanese wet contaminated cloth (116, 2 sheets/L)

[0089] 3. Amount of sample: Standard amount 0.09 g/L

[0090] 4. The contaminated cloth and a predetermined amount of sample are introduced to IL of water, agitated for 10 minutes and evaluated (each contaminated sheet is evaluated separately).

[0091] 5. A change in Wb value of each contaminated cloth is determined by using a color difference meter and the cleaning power is calculated by using the Harris formula.

[0092] 6. The cleaning power right after the manufacture of each sheet is taken as 100 to determine a change in cleaning power.

[0093] * The stored sample is stored in a package made of PET16+LLDPE55 for 4 weeks.

[00001]$\mathrm{Cleaning}\mathrm{power}\left(\%\right)=\frac{\left[{\left(1-R_S\right)}^2/2R_S\right]-\left[{\left(1-R_b\right)}^2/2R_b\right]}{\left[{\left(1-R_S\right)}^2/2R_S\right]-\left[{\left(1-R_0\right)}^2/2R_0\right]}\times 100$

[0094] wherein R.sub.s represents the surface reflectivity of contaminated cloth before washing; R.sub.b represents the surface reflectivity after washing; and R.sub.D represents the surface reflectivity of white cloth.

[0095] Referring to FIG. 4, the sheet including 15 wt % of sorbitol according to Example 3 maintains the same cleaning power as the cleaning power upon the initial manufacture, even after storing it for 4 weeks. However, the sheet including no sorbitol shows cleaning power reduced by about 40%.

[0096] It is thought that when using sorbitol, storage stability is reinforced to prevent degradation of cleaning power caused by decomposition of soda ash (sodium carbonate), and thus there is no difference in cleaning power between the sheet right after the manufacture and the sheet after the storage at room temperature. However, the scope of the present disclosure is not limited to this theory.

Method for Evaluating Dissolution Rate of Soluble Sheet

Test Method

[0097] Each of the samples according to Examples and Comparative Examples was prepared with a size of 6×6×0.12 cm.sup.3, water was prepared at 25° C. in a constant-temperature/constant-humidity chamber under the condition of 20° C. and 30%, and then a squared water bath having a size of 25 cm×30 cm was filled with water to a waver level of 5 cm.

[0098] Next, each sample was allowed to float in water, and the time required for crumbling without agitation was measured as an average value of five measurements. When the time required for accomplishing dissolution is within 30 seconds, the sheet is evaluated as ‘very good’. When the time is 30 seconds to 3 minutes and 3-5 minutes, the sheet is evaluated as ‘good’ and ‘fair’, respectively. In addition, when the time is 5-10 minutes and 10 minutes or more, the sheet is evaluated as ‘poor’ and ‘very poor’, respectively.

[0099] Criteria for judgement of dissolution: When filtering is carried out with a 75 μm filter and the weight of the non-filtered residual detergent is less than 5% based on the total weight of the detergent, the sheet is judged as ‘dissolved’.

[0100] The results of Comparative Example 1 and Example 3 are shown in FIG. 5. When using a polyol, dissolution rate is increased significantly. The top view of FIG. 5 illustrates the dissolution rate of the sheet according to Comparative Example 1, and the bottom view illustrates the dissolution rate of the sheet according to Example 3.

Method and Criteria for Evaluating Mass Productivity of Laundry Sheet

Method for Evaluating Mass Productivity

[0101] 1. After the product is dried in a factory, the product is determined whether it is broken or not upon the separation from the release sheet.

[0102] 2. When drying 800 kg of a blend and the sheet is wound on a rewinder without failure, the sheet is evaluated as ‘good’. When the sheet is broken during rewinding, it is evaluated as ‘poor’, and when the sheet is broken before rewinding, it is evaluated as ‘very poor’.

Method for Evaluating Tensile Strength

[0103] 1) A sample having a width of 20 mm, length of 60 mm and a thickness of 1.2 mm is prepared.

[0104] 2) The tensile strength of the sample is measured by using 500N zwicki; Zwick Roell in a constant-temperature/constant-humidity chamber under the condition of 20° C. and 30%.

[0105] 3) The sample is fixed with an interval between grips of 25 mm, and then the tensile strength is measured by moving the sample at a speed of 500 mm/min until it is broken.

Test Result

[0106]

TABLE-US-00003 TABLE 3 Tensile strength Evaluation of mass Content of sorbitol (kgf/cm.sup.2) productivity 0% (Comp. Ex. 1) 2.805 Good 10% (Ex. 2) 1.890 Good 15% (Ex. 3) 1.595 Good 20% (Comp. Ex. 3) 0.825 Poor

[0107] 1. After carrying out the test three times, the average value is recorded.

[0108] 2. As the content of sorbitol is increased, the tensile strength tends to be decreased.

[0109] In addition, the tensile strength is decreased dramatically from a content of sorbitol of 20%.

[0110] 3. At a content of 20% or less, mass production is allowed without failure during rewinding. When sorbitol is used in an amount of larger than 20%, the sheet is broken before rewinding and during the separation of the sheet, and thus cannot be produced as a commercial product.

Increase in Active Ingredients of Soluble Sheet and Evaluation of Cleaning Power

[0111] It is determined whether or not the sheet can be formulated and has improved storage stability and solubility even with a small amount of formulating agent, when using sorbitol. Therefore, a change in proportion of active ingredients, a possibility of increasing the amount of active ingredients and a change in cleaning power caused thereby were determined by using sorbitol.

TABLE-US-00004 TABLE 4 Comp. Comp. Comp. Ex. 1 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 8 Formulating agent (PVA) 40 45 20 20 20 18 Sorbitol 15 15 15 15 15 Detergent ingredient (SLS) 50 30 50 52 54 54 Builder (Na.sub.2CO.sub.3) 7 7 12 10 8 10 Enzyme 2 2 2 2 2 2 Others (fragrance etc., not 1 1 1 1 1 1 affecting cleaning power) Total 100.0 100.0 100.0 100.0 100.0 100.0 Change in combined weight −20 +5 +5 +5 +7 of detergent ingredient and laundry aid Formulation Good Good Good Good Good Poor Solubility Fair Poor Very Good Very Good Very Good Very Good Storage stability Fair Fair Very Good Very Good Very Good Very Good Cleaning power — Decreased as Increased Increased Increased Increased compared to by at most by at most by at most by at most Comp. Ex. 1 about 30% as about 30% as about 30% as about 30% as compared to compared to compared to compared to Comp. Ex. 1 Comp. Ex. 1 Comp. Ex. 1 Comp. Ex. 1

Determination of Change in Cleaning Power

[0112] 1. Terg-o-tometer, water IL, water temperature 20° C., hardness 50 ppm

[0113] 2. Used contaminated cloth: Japanese wet contaminated cloth (JIS, 8 sheets/L), w-20D (20D, 8 sheets/L), empa 116 (116, 2 sheets/L), empa-117 (117, 2 sheets/L)

[0114] 3. Amount of sample: Standard amount 0.09 g/L

[0115] 4. The contaminated cloth and a predetermined amount of sample are introduced to IL of water, agitated for 10 minutes and evaluated (each contaminated sheet is evaluated separately).

[0116] 5. A change in Wb value of each contaminated cloth is determined by using a color difference meter and the cleaning power is calculated by using the Harris formula.

[00002]$\mathrm{Cleaning}\mathrm{power}\left(\%\right)=\frac{\left[{\left(1-R_S\right)}^2/2R_S\right]-\left[{\left(1-R_b\right)}^2/2R_b\right]}{\left[{\left(1-R_S\right)}^2/2R_S\right]-\left[{\left(1-R_0\right)}^2/2R_0\right]}\times 100$

[0117] wherein R.sub.s represents the surface reflectivity of contaminated cloth before washing; R.sub.b represents the surface reflectivity after washing; and R.sub.D represents the surface reflectivity of white cloth.

[0118] When increasing active ingredients, the cleaning power is increased by about 10% or more as compared to the conventional product in all of the contamination cases. Particularly, in the case of contamination with protein, the cleaning power is increased by about 30%. The results are shown in FIG. 6.

Evaluation of Solubility of Water-Soluble Laundry Sheet Including Both Sodium Chloride and Polyol

[0119]

TABLE-US-00005 TABLE 5 Ex. 11 Formulating agent (PVA) 31 Polyol (sorbitol) 4.5 Chloride (sodium chloride) 4.5 Detergent ingredient (SLS) 50 Laundry aid (builder, enzyme, etc.) 9 Others (fragrance etc.) 1 Total 100.0 Formulation Good Dissolution rate Very Good

[0120] When using both sorbitol and sodium chloride, the dissolution rate is improved significantly.

2. Manufacture of Soluble Sheet Including Metal Ion Chloride

Manufacture of Soluble Sheet Including Sodium Chloride (Salt)

[0121] First, a blend was prepared by introducing a formulating agent as a water-soluble film-forming polymer, a sodium chloride, a detergent ingredient, a laundry aid and other ingredients, in turn, to water at 60° C., wherein agitation was carried out at 180 rpm until the introduced ingredients were dissolved completely in each introduction step. Herein, the amount of water was the same as the combined weight of the formulation agent +sodium chloride+detergent ingredient+laundry aid+other agents (50% aqueous solution was prepared).

[0122] In the formulation process, the blend was formed into a sheet having a size of 15×25 cm and a thickness of 1.5 mm with a doctor blade, and then the sheet was dried in a drying oven at 125° C. for 12 minutes.

Evaluation of Formulation of Water-Soluble Laundry Sheet

[0123] The following test was carried out.

[0124] After each sheet is prepared, it is observed whether the phenomena as shown in FIG. 1 and FIG. 2 occur or not. In other words, each sheet is observed whether or not it is attached to the release sheet after the manufacture to prevent its separation from the release sheet, and then whether or not each sheet is broken upon the detachment from the release sheet.

[0125] The test was carried out in a constant-temperature/constant-humidity chamber under the condition of 20° C. and 30%. Each sheet is manufactured five times repeatedly.

[0126] When all of the phenomena are not observed, the sheet is evaluated as ‘good’. When the phenomenon as shown in FIG. 1 is observed, the sheet is evaluated as ‘poor’. In addition, both of the phenomena as shown in FIG. 1 and FIG. 2 are observed, the sheet is evaluated as ‘very poor’.

[0127] As can be seen from the following test result, a water-soluble laundry sheet obtained by adding a metal ion chloride shows less problem of adhesion to a release sheet or sheet breakage. In other words, addition of a metal ion chloride positively affects the formulation of a sheet.

TABLE-US-00006 TABLE 6 Comp. Comp. Comp. Ex. 9 Ex. 12 Ex. 13 Ex. 14 Ex. 10 Ex. 11 Formulating agent (PVA) 40 37 35 30 28 25 Metal ion chloride (salt) 3 5 10 12 15 Detergent ingredient (SLS) 50 50 50 50 50 50 Laundry aid (builder) 7 7 7 7 7 7 Enzyme 2 2 2 2 2 2 Others (fragrance etc., not 1 1 1 1 1 1 affect cleaning power) Total 100.0 100.0 100.0 100.0 100.0 100.0 Solubility Fair Fair Very Good Very Good — — Formulation Good Good Good Good Poor Poor Storage stability Fair Good Very Good Very Good — —

Evaluation of Stability with Time through IR

[0128] A water-soluble laundry sheet made by using PVA is problematic in that decomposition of a detergent ingredient and laundry aid is accelerated with time due to the decomposition of PVA. Thus, it is determined whether addition of salt improves storage stability or not. The result is shown in FIG. 7.

[0129] The blend for a laundry sheet having the following composition and prepared as 50% aqueous solution was analyzed by IR spectrometry.

[0130] Right after manufacturing the sheet, IR was measured. Then, IR was further measured after storing (20° C., 30%, stored in a package made of PET 16+LLDPE55) the sheet for 4 weeks (test instrument: Perkin Elmer ultra two, constant-temperature/constant-humidity chamber, temperature 20° C., humidity 70%).

[0131] Referring to the result of FIG. 7, the IR peak of active ingredients causes a change, when salt is added. Particularly, as shown in FIG. 8a and FIG. 8b, it can be seen that there is little difference in peak of active ingredients, when salt is added in an amount of 5 wt % based on the dry weight of the sheet. Therefore, it can be seen that addition of salt assists stability of active ingredients and enhances improvement of cleaning power.

Method for Evaluating Dissolution Rate of Soluble Sheet

Test Method

[0132] Each of the samples according to Examples and Comparative Examples was prepared with a size of 6×6×0.12 cm.sup.3, water was prepared at 25° C. in a constant-temperature/constant-humidity chamber under the condition of 20° C. and 70%, and then a squared water bath having a size of 25 cm×30 cm was filled with water to a waver level of 5 cm.

[0133] Next, each sample was allowed to float in water, and the time required for crumbling without agitation was measured as an average value of five measurements. When the time required for accomplishing dissolution is within 30 seconds, the sheet is evaluated as ‘very good’. When the time is 30 seconds to 3 minutes and 3-5 minutes, the sheet is evaluated as ‘good’ and ‘fair’, respectively. In addition, when the time is 5-10 minutes and 10 minutes or more, the sheet is evaluated as ‘poor’ and ‘very poor’, respectively.

[0134] Criteria for judgement of dissolution: When filtering is carried out with a 75 μm filter and the weight of the non-filtered residual detergent is less than 5% based on the total weight of the detergent, the sheet is judged as ‘dissolved’.

[0135] The result is shown in FIG. 9. It can be seen from the result that when a laundry sheet is manufactured by adding 5 wt % of salt, the laundry sheet shows a significantly increased dissolution rate as compared to the sheet including no salt.

Effect of Improving Dissolution Rate Depending on Type of Metal Ion Chloride

[0136] To determine how the dissolution rate of a sheet is changed depending on the type of a chloride, the following test was carried out. In the following table, each content is expressed in the unit of wt %.

TABLE-US-00007 TABLE 7 Ex. 15 Ex. 16 Ex. 17 Comp. Ex. 12 Type NaCl CaCl.sub.2 MgCl.sub.2 Na.sub.2SO.sub.4 Formulating 30 30 30 30 agent (PVA) Metal ion 10 10 10 10 chloride Detergent 50 50 50 50 ingredient (SLS) Laundry aid 7 7 7 7 (builder) Enzyme 2 2 2 2 Others 1 1 1 1 (fragrance etc., not affect cleaning power) Solubility Very Good Good Fair Good Formulation Good Good Good Good Storage stability Very Very Very Fair Good Good Good Total 100.0 100.0 100.0 100.0

[0137] Each of the water-soluble laundry sheets having the compositions as shown in Table 7 was manufactured and evaluated in terms of its dissolution rate according to the above <Method for Evaluating Dissolution Rate of Soluble Sheet>. In the case of the water-soluble laundry sheet (Comparative Example 12) including a sulfate, the sheet is little dissolved even after the lapse of 50 seconds, when being tested according to the above method. On the contrary, it can be seen that each of the water-soluble laundry sheets including a chloride according to Examples 15-17 is dissolved in washing water at a significantly high rate.

INDUSTRIAL APPLICABILITY

[0138] The present disclosure provides a sheet-like laundry detergent that is dissolved in water and can be used conveniently. The sheet-like laundry detergent according to the present disclosure shows high solubility and excellent storage stability.