EP0947579B1

EP0947579B1 - Process for producing transparent solid soap or transparent soap stock

Info

Publication number: EP0947579B1
Application number: EP97939200A
Authority: EP
Inventors: Isao c/o Pola Chemical Industries Inc. SHIMOSATO; Masanori Pola Chemical Industries Inc. OKADA
Original assignee: Pola Chemical Industries Inc
Current assignee: Pola Chemical Industries Inc
Priority date: 1997-09-05
Filing date: 1997-09-05
Publication date: 2006-06-07
Anticipated expiration: 2017-09-05
Also published as: AU720810B2; EP0947579A1; DE69736071D1; EP0947579A4; CA2270381A1; DE69736071T2; WO1999013041A1; AU4135897A

Description

The present invention relates generally to a method of making a transparent solid soap and, more particularly, to a transparent solid soap which can be easily produced without requiring a fine control of water content and a maturing period till reduction in weight is settled and, besides, exhibits high stabilities of transparency and weight with passage of time.
A transparent soap is visually beautiful and excellent in terms of safety and detergency, and is therefore widely used as a detergent. Generally, the transparent soap is mixed with a moisture-absorbing component as an indispensable component such as polysaccharide, and the like in order to create the transparency and mixed, in addition, with a volatile component such as ethanol, and the like.
The transparent solid soap, however, declines in terms of transparency when the moisture-absorbing component absorbs the moisture content, and it is therefore required that fine control of the water content be precisely made by a hot roll while monitoring the transparency and the water content. Further, when mixed with a volatile component, the volatile component volatilizes, resulting in a decrease in weight. Hence, a maturing period as long as several weeks to several months is needed till the decrease in weight is settled. Namely, it is quite troublesome to execute the control so as to exhibit high transparency and high stabilities of transparency and of weight with passage of time in terms of manufacturing the transparent solid soap.
Moreover, if processed as a soap with a stripe pattern by use of a conventional transparent soap material together with other opaque soap materials, the transparency of the transparent soap portion is spoiled by the moisture content contained in the opaque soap, which leads to a drawback in which the stripe pattern becomes blurred. Furthermore, some of the currently used transparent solid soaps are mixed with sorbitol defined as polysaccharide in order to enhance the transparency. Sorbitol is, however, crystal-deposited as time elapses enough to make the transparent soap cloudy, and it happens often that the stability of transparency with the passage of time might be spoiled.
EP-A-0 335 026 discloses a transparent soap bar which requires the components to fit within three critical ratios, and which comprises a mixture of alkanolammonium and alkali metal C₁₂-C₂₂ atom fatty acid salts, and a solvent system.
Under such circumstances, there has been demanded a transparent soap that can be easily produced without requiring fine control of the water content and a maturing period and, besides, exhibits high stabilities of transparency and of weight with the passage of time.
On the other hand, it has already been practiced that a transparent solid soap is mixed with an organic amine such as triethanolamine, but high-concentration mixing has not been carried out. Further it was not known that a transparent solid soap which can be easily produced and exhibit high stability are obtained by mixing with organic amine such as triethanolamine at a high concentration
The present inventors have obtained a soap that remains transparent even when polysaccharide and alcohol are not present which involves including sodium hydroxide and an organic amine in a predetermined ratio as the alkali for saponification and specifying the quantity of alkali as a predetermined saponifying equivalent of the fatty acid, and have found that this transparent soap is easy to produce and exhibits good stability.
Thus, according to the invention we provide a method of making a transparent solid soap by saponifying fatty acid or animal/vegetable oil with alkali in the absence of alcohol, which comprises mainly a salt of fatty acid, wherein

(1) said alkali is sodium hydroxide and organic amine, and the molar ratio of said sodium hydroxide to said organic amine is from 1:0.8 to 1:1.8, and
(2) the quantity of said alkali is 2.2 to 2.7 saponifying equivalents of said fatty acid or said animal/vegetable oil,

It is particularly preferable that the organic amine is triethanolamine.
Note that the term "transparent" implies a state of being substantially clear with slight turbidity as well as implying that transmissivity of visible light is approximately 25% or above. Moreover, the term "transparent" is not limited to achromatic transparency.
The term "saponifying equivalent" means the minimum alkali quantity needed for transforming all of the fatty acid or animal/vegetable oil into a salt of the tatty acid, i.e., into a soap, and the quantity thereof should be regarded as 1 saponifying equivalent.
The transparent solid soap obtained by the method of the present invention does not contain a polysaccharide such as sorbitol or alcohol such as ethanol as indispensable components. Accordingly, the soap rarely becomes turbid as a result of moisture absorption or crystal deposition, and the like, which happen with a soap comprising polysaccharide, and is excellent in terms of stability of transparency over the passage of time. Moreover, the transparent solid soap prepared according to the present invention is easy to produce for the reason that the labor for controlling moisture content is reduced because of the absence of moisture-absorbing components such as polysaccharide, and that a maturing period until the content of a volatile component such as alcohol has reached equilibrium is not required.
The present invention will hereinafter be described in detail.
The organic amine component of the soap produced by the method of the invention may for example be diethanolamine, triethanolamine, triethylamine, trimethylamine or diethylamine. Triethanolamine is particularly preferable. A single organic amine may be used, or two or more organic amines may be employed in combination.
The alkali quantity corresponding to 1 saponifying equivalent, for example, can be obtained as the alkali quantity necessary for neutralizing the acid derived from the fatty acid, calculating the acid quantity from the weight and the molecular weight of the fatty acid.
The fatty acid or the animal/vegetable oil used for the transparent solid soap according to the present invention may be those generally employed as fundamental sources. As the fatty acid, there can be specifically exemplified stearic acid, lauric acid, myristic acid, palmitic acid and behenic acid and the like. Synthetic or natural fatty acids may be used. Further, as the animal/vegetable oil, specifically, beef tallow, coconut oil and hydrogenated coconut oil, and the like, which is previously hydrolyzed into the fatty acid, may be used or may be used intact.
Further, the quantity of the fatty acid used as a raw material for the transparent solid soap according to the present invention is preferably from 30% to 60% by weight, more preferably from 35% to 57% by weight and, much more preferably, from 37% to 55% by weight. Moreover, the quantity of triethanolamine used is preferably from 30% to 50% by weight, more preferably from 31% to 47% by weight, and even more preferably from 32% to 45% by weight. Furthermore, the quantity of sodium hydroxide used is preferably from 5% to 10% by weight, more preferably from 5.5% to 9.5% by weight, and much more preferably from 6% to 9% by weight.
In the transparent solid soap according to the present invention, if in such a range as not to spoil the effects of the present invention, there can be optional components generally used for the soap in addition to the indispensable components described above. As the above optional components, there may be exemplified, e.g., antioxidant such as BHT, chelating agent such as EDTA and hydroxyethane diphosphonic acid, antiseptic agent such as methylparaben, coloring matters, pigments, fine particles, mica titanes with interference colors, pearl agent such as mica titanes, perfume, and surface active agent such as POE added sodium alkylsulfate.
Although the transparency might be reduced to some extent by the inclusion of such optional components, and depending on the quantity added, the soap can become highly lustrous and conspicuous in colour.
The transparent solid soap according to the present invention can be manufactured by an ordinary transparent solid soap manufacturing method. For example, the transparent solid soap can be manufactured by a frame kneading method of saponifying the fatty acid or the animal/vegetable oil with alkali, melting a mixture by heating that are mixed with other components as the necessity arises, pouring the mixture into a mold and solidifying it by cooling.
Moreover, the transparent solid soap can be obtained by carrying out pellet processing such as pressurization-molding, i.e., by a mechanical kneading method. Further, if pressurization-molded by use of the pellet into which the transparent soap material of the present invention is molded and the pellet manufactured from an ordinary opaque soap material, a transparent solid soap having a stripe pattern is to be obtained. Moreover, a flower-shaped molding is made of an opaque soap and embedded in and wrapped with the transparent soap material of the present invention by the frame kneading method, thereby making it possible to obtain a transparent solid soap with the molding embedded in and wrapped therewith. Further, if a printed thin film composed of carboxymethylcellulose is embedded in and wrapped therewith, it is feasible to obtain the transparent solid soap with a picture drawn inside.
The present invention will hereinafter be described in detail by means of non-limiting Examples. Note that numerical values of prescription are parts by weight as far as no particular indications are given.

Examples 1 - 6

The transparent soap material is manufactured according to the formulation of Table 1 which follows. Concretely, the components of Table 1 are scale-put into a heating kneader, kneaded for 2 hours at 80°C, and, through a pelletizing operation by a hot roll and a pelleter, the transparent soap material is obtained as a pellet. When the moisture content of this pellet is obtained by Karl Fischer moisture content titration , the moisture content of the pellet comes to the result shown in Table 1. When the component composition of the pellet is calculated from this moisture content, the component composition as shown in Table 2 is obtained. Note that the quantity of alkali with respect to fatty acid is as shown in Table 3.

Table 1

Component	Example 1	Example 2	Example 3
Coconut oil fatty acid	40	40	40
Beef tallow fatty acid	160	160	160
Triethanolamine	140	145	160
Sodium hydroxide	34	29	26
Water	86	81	79

State of pellet	Transp a-rent solid-state	Transp a-rent solid-state	Transp a-rent solid-state
Pellet moisture content (weight %)	5.4	6.2	4.8

Component	Example 4	Example 5	Example 6
Coconut oil fatty acid	40	40	40
Beef tallow fatty acid	160	160	160
Triethanolamine	170	175	160
Sodium hydroxide	34	26	31
Water	86	79	84

State of pellet	Transp a-rent solid-state	Transp a-rent solid-state	Transp a-rent solid-state
Pellet moisture content (weight %)	6.1	5.5	5.6

Table 2

Component	Example 1	Example 2	Example 3
Coconut oil fatty acid	10.2	10.0	9.7
Beef tallow fatty acid	40.9	40.1	39.5
Triethanolamine	35.8	36.4	39.5
Sodium hydroxide	8.7	7.3	6.4
Water	4.4	6.2	4.8

Component	Example 4	Example 5	Example 6
Coconut oil fatty acid	9.3	9.4	9.7
Beef tallow fatty acid	37.2	37.7	38.6
Triethanolamine	39.5	41.3	38.6
Sodium hydroxide	7.9	6.1	7.5
Water	6.1	5.5	5.6

Table 3 (Unit: Saponifying Equivalent)

	Alkali quantity to fatty acid
Example 1	2.37
Example 2	2.24
Example 3	2.28
Example 4	2.65
Example 5	2.41
Example 6	2.45

Examples 7 - 12

The transparent solid soap is obtained by pressure-forming the pellet-like transparent soap material in the Examples 1 - 6. In this transparent solid soap,the change in weight is less than 5% even when preserved at 40°C for one month, and, further, neither variation in the transparency nor crystal deposition can be seen.

Example 13

The transparent soap material is manufactured according to the scaling prescription in Table 6 which follows. Concretely, the prescription components in Table 6 are scale-put into a heating kneader, kneaded for 2 hours at 80°C, and, through the pelletizing operation by a hot roll and a pelleter, the transparent soap material is obtained as a pellet. Note that according to the prescription in Table 6, the alkali quantity relative to the fatty acid is 2.45 saponifying equivalents.
The moisture content of this pellet was 5.1% by weight (which is based on the Karl Fischer moisture content titration). This pellet was a lustrous white solid body. This soap material showed no variation in weight even when preserved at 40°C for one month Table 6 (Scaling Prescription)

Component Mixing quantity

Stearic acid 30

Palmitic acid 13

Sodium hydroxide 6.7

Triethanolamine 32

BHT 0.1

Hydroxyethane diphosphonic acid 0.1

Water 17.1

Titanium oxide 1

Example 14

The transparent soap material is manufactured according to the scaling prescription in Table 7 which follows. Concretely, the prescription components in Table 6 are scale-put into a heating kneader, kneaded for 2 hours at 80°C, and, through the pelletizing operation by a hot roll and the pelleter, the transparent soap material is obtained as a pellet. Note that according to the prescription in Table 7, the alkali quantity relative to the fatty acid is 2.45 saponifying equivalents.
The moisture content of this pellet was 5.1% by weight (which is based on the Karl Fischer moisture content titration). This pellet exhibited no change both in the weight and the transparency even when preserved at 40°C for one month. Table 7 (Scaling Prescription)

Component Mixing quantity

Stearic acid 30

Palmitic acid 13

Sodium hydroxide 6.7

Triethanolamine 32

BHT 0.1

Hydroxyethane diphosphonic acid 0.1

Water 18.1

Example 15

The pellet in the example 13 is melted by heating, poured into a silicone rubber mold and solidified, thus manufacturing a molding of a flower of rose. This molding is placed in a frame, and the transparent soap material molten by heating in the example 14 is softly poured and solidified by cooling, thus obtaining a transparent solid soap including a flower. This transparent solid soap exhibited neither a change in the transparency of the transparent portion nor a change in weight even when preserved at 40°C for one month.

Industrial Applicability

The transparent solid soap according to the present invention can be easily produced without requiring fine control of the moisture content or a maturing period till reduction in weight has been settled, and, besides, exhibit high stabilities of transparency and of weight with the passage of time.

Claims

A method of making a transparent solid soap by saponifying fatty acid or animal/vegetable oil with alkali in the absence of alcohol, which comprises mainly a salt of fatty acid, wherein
(1) said alkali is sodium hydroxide and organic amine, and the molar ratio of said sodium hydroxide to said organic amine is from 1:0.8 to 1:1.8, and

(2) the quantity of said alkali is 2.2 to 2.7 saponifying equivalents of said fatty acid or said animal/vegetable oil,
so as to obtain a transparent soap material, and pouring said material into a mold and solidifying it by cooling.
A method according to claim 1, wherein said organic amine is triethanolamine.