PROCESS FOR PREPARING CARRIERS SATURATED OR COATED WITH MICROENCAPSULATED SCENTS

Abstract: The invention refers to the process of preparation of carriers, impregnated or coated with microencapsulated scents, comprising the preparation of microcapsule emulsion, preparation of coating and coating or impregnation of carrier. After the preparation of emulsion it also includes emulsifying of core material into a solution of wall material base containing modifier. Such processes also comprise initiation of wall formation by raise of temperature and/or change of pH value and in addition to that also finishing or interrupting the reaction in microencapsulation by changing the pH value by which polymerization stops. According to the invention during the preparation of microcapsule emulsion in the stage of preparation of core material water for the extraction of water soluble components is emulsified into solution of essential oils and after the extraction separated from oil for which the presumed essential oils or presumed scents, especially natural essential oil, synthetic scents or their mixture, either pure or diluted with adequate solvents such as phalates, myristinats, adipates, higher non-aromatic hydrocarbons are microencapsulated and where water-soluble components are extracted from the solution of essential oils in solvents by means of water and in addition to that, during the initiation of wall, temperature is gradually increased from the value which corresponds to approximately 50 % value of temperature volatility of each essential oil or a scent to the temperature of which value is approximately 90 % value of temperature volatility of each essential oil or scent. Microencapsulated scent, binders, organic and/or inorganic pigments and fillers, anti-foaming agents for viscosity regulation are added for the preparation of coating or impregnating mixture, depending on the carrier. When coating or impregnating the carrier the coating in a form of suspension is applied by means of scraper, air knife, cylinders; when impregnating the carrier, which is a woven or non-woven material, paper, cardboard or foil of artificial material, it is transferred through the saturation basin containing impregnating mixture.

Description: Process for preparing carriers saturated or coated with microencapsulated scents The invention refers to the process for preparing of carriers saturated or coated with microencapsulated scents. According to international patent classification this invention can be ranged in the field of treatment, especially treatment of chemical procedures (B 01J 13/02), as well as in the field of textile (D06 Ml 5/04) or paper (D21 H27/36). The invention is based on the problem to create a process for preparing of carriers, either saturated or coated with microencapsulated scents, by means of which it will be possible to obtain such carriers, either saturated or coated with microencapsulated scents, where evaporation of scent and impact of the environment to the scent or to its sensitive components will be prevented and thus the need of environmental unfriendly, impermeable packaging for such carriers will be eliminated. At the same time, and instead of unwilling permanent and therefore short effect of scents, the willing and thus long- lasting effect of scents will be provided by which the durability of the carriers obtained by this process will be prolonged. Carriers saturated with free scents (e.g. essential oils) are widely used. Refreshing tissues, deodorizing or antiseptic shoe insoles, deodorizing towels, paper sheets for promotion and advertising of scents and similar products have already been known. They are usually made by the process of saturation or impregnation of a carrier with scents. As the scents are volatile it is necessary to pack articles produced by such process into special impermeable packaging which is not environmental friendly. In spite of impermeable packaging the problems emerge later when the packaging is opened. The problem is not so evident with articles that are intended for instant or single use as it is with durable products, i.e. deodorizing shoe insoles where durability of a product weakens quickly due to the volatile character of scents. In addition to the above mentioned problem of packaging and durability with the products obtained according to previously mentioned method of saturation with scents we are also encountered with certain practical problems, such as product dampness to the feel. uncontrolled release of the essence as well as exposure of scents to the negative impact of the environment, especially to light, temperature and air. In the past there were different solutions applied for previously mentioned problems. One of them is a process where a scent is bound to certain adsorbents which does slow down the scent release but the scent also remains unprotected against the environmental effects. Further on, such process of microencapsulation are known according to which slow release of a scent or scent composition is achieved and at the same time it is protected against negative impact of the environment. The process of microencapsulation in general provides coating the emulgated particles (i.e. solvents or leuco dyes) and thus preparation of microcapsules of various characteristics and for various application purposes. Microcapsules produced in such way can be applied in various fields, e.g. (US 2,730,456; US 4,100,103; US 474,379; EP 107.957) for manufacturing of carbonless copy papers, for preparation of microencapsulated pesticides with controlled release for agricultural application (GB 1,581,255; EP 17.409; YU 3109; EP 51.161), for separation of reactants (DE 2.247.468; US 4,536,524) of double-component glues, in mariculture (GB 2,040,863) for preparation of food for larvae as well as in medicine for taste masking of certain medicaments and/or for their controlled release (US 3,860,733). In general, microencapsulation can be performed by mechanical or chemical processes, the latter being more appropriate as they enable changing of wall characteristics. Chemical procedures of microencapsulation can be classified in three groups, i.e. coacervation, interfacial polycondensation or polymerization and polymerization or polycondensation "in situ". For the process of coacervation (e.g. US 2,800,457; US 2.730.456; GB 2,099,847; EP 58.430; GB 2,122,630; DE 3.424J 15, DE 2J00.700 and FR 2.570.604) gelatine in combination with gum Arabic or other anion polymers such as carboxymethylcellulose, polyacrylic acid, maleic anhydride copolymer similar substances are most frequently used as wall material. The main deficiency of such procedures is that gelatine is a natural substance, therefore the input material characteristics can vary and further coacervation can be performed only at low concentration of water solutions which means long-lasting and technically demanding procedures and microcapsule walls obtained by such procedure possess poor mechanical properties unless additionally treated. When microencapsulating by interfacial polymerization (e.g. EP 107.957, US 4.324.817, EP 16.378, DE 3.421.865, GB 1.581.255, US 4.228.216, DE 3.635.821, US 3.429.827, US 4.000.087 and US 4.768.048) the wall forming reactants are present both in the oil (hydrophobic) as well as in the water (hydrophilic) phase. The microcapsule wall is formed on the border between the phases oil/water, therefore the wall thickness of all microcapsules is in proportion with the microcapsule size, while microcapsules obtained by the process of coacervation or polycondensation "in situ" have walls of the same thickness. This circumstance undoubtfully represents certain advantage but unfortunately, it is difficult to prepare microcapsules which would at the same time also possess walls of good mechanical properties. The wall itself, when it starts to form (for which the reacting pairs of polyol/isocyanate, polyamine/isocyanate and polyhydroxy/epoxy compound can be considered) renders the contact between the reactants difficult so that -further reaction process depends on the possibility of diffusion through already created wall. The consequences of the above are inevitable deficiencies of such procedures manifested mainly through the reactiveness of reactants, incomplete reactions, and also a possibility of reaction with one of the core components which is the reason that many substances cannot be microencapsulated by means of such process. When microencapsulating by the process "in situ" (especially "in situ" polymerization or polycondensation of amino-formaldehyde resins e.g. US 4,001,140; US 4,100,103; CA 1,108,944; US 4,675,249; EP 826.635; EP 133.295; EP 237.054; DE 3.626J87; DE 3.532.878; JP 137.852; DE 3.709.586; YU 18623-P-1319/84) all the available material for walls originates merely from the (continuous) water phase. In case of ideal procedure conditions all the wall material which can be precipitated by the known process, for example by change of pH or temperature, would be distributed evenly over the complete microcapsule surface, therefore the wall being of the same thickness - regardless the size of microcapsules. Amino-formaldehyde resins (melamine-formaldehyde and urea- formaldehyde or their mixtures) were mainly used as wall material. Some older process (according to GB 1,301,052; or GB 1,156,725) and some newest (DE 3.709.586 or US 4,333,849) are difficult to perform and were therefore replaced, especially in the phase of forming or stabilizing the wall, with process characterized by the presence of (modifiers) which primarily serve as emulsifier, and further on initiate polycondensation of amino-component and aldehyde component or amino-formaldehyde precondensate in a specific way (so that polymerization develops only on the surface of emulsified oil drops and not throughout the whole water phase), further on they adapt the role of a binder to the base after finished polymerization. Presence of modifiers results in simpler procedure control and also in good mechanical properties of microcapsules. If compared with a procedure of coacervation, for instance with a procedure of interfacial polymerization then the process of polymerization "in situ" is technologically easier to perform, and in addition to that this process provides microcapsules with better mechanical properties and the microcapsule emulsion possesses high percentage of dry substance at low viscosity. Microencapsulation of scents, especially essential oils, can be performed by microencapsulation "in situ" as described in YU 18623 (P-1319/84). The quoted process was performed so that the oil solution of leuco dyes containing additive (a compound or mixture of compounds one or more functional groups such as -OH, NH 2 , NH-R, COOH, CONH 2 , CONH-R, where R stands for C t - C 4 alkyl radical are bound to saturated C 9 -C 18 hydrocarbone radical) and that in quantity from 0,1 to 30 mass % of additive regarding the mass of oil dye were emulsified in the water solution of modifier (eg. polyacrilyc acid, copolymer ethylene and maleic anhydride or copolymer styrene and maleic anhydride and a mixture of those) in a quantity of 1-15 mass % of modifier regarding the oil dye in and then amino-formaldehyde precondensate, such as di to hexamethylol melamin or di to terra methylol urea, methylated methylol melamin or metyhated methylol urea and their low polycondensed products (where the degree of methylation of methylated methyol melamin or methylated methyol urea was from 0-100%, ratio between modifier and amino formaldehyde precondensate was from 10:1 to 1:1) which polymerizate (polycondensate) at increased temperature (50-100°C) and at pH from 4 - 7 and walls the emulsion of leuco dyes were added. If in case of microencapsulation of scents according to the above process we use scents, e.g. essential oil, instead of leuco dyes, then the application of this process for microencapsulation of scents unfortunately and inevitably brings certain deficiencies manifested mostly in different distribution of emulsion particles (ace. to size) and walled oil particles - microcapsules - is different which is mostly related to irregularities in the phase of wall formation. Further deficiencies are poor physical properties (especially mechanical resistance) of microcapsules produced by such process. In this case the microcapsule emulsion viscosity is also higher as it is in case when leuco dye is microencapsulated, unfavourable agglomerates or "clusters" of microcapsules are formed and they are not welcome when coating paper or any other carrier, therefore the majority of scents cannot be microencapsulated by this process or applied to the carrier that could be practically used in a form of microcapsules. In general, water-soluble components of scents (with functional groups -OH, -NH, -CO, -CHO or COOH) disturb the course of microencapsulation already in small quantities. On one hand they can change into water phase during emulsifying where local precipitation of emulsifier and thus change of particle size can appear due to reduced emulsifying capacity, which is even intensified during the heating to the polymerization temperature as the solubility of acids at raised temperature is even higher, which renders the accumulating of polymerized resin to the surface of oil particles even more difficult. On the other hand uncontrolled polymerization of armno-aldehyde resin in the mass or reaction with the amino-aldehyde resin can occur and, due to that, physical (especially mechanical) properties of the wall are changed. One of the solutions how to solve the previously mentioned problem is to eliminate free acids and water-soluble components from the scent composition before the emulsifying phase which can be realized by multiple water extraction, the consequence of which is that free acids and water soluble components are distributed in hydrophobic and hydrophilic phase (in accordance with the Henry's partition law). Further process is described in Yugoslav patent P-1319/84, the supplement of which is the process according this invention. According to the invention the process of preparation of carriers, saturated or coated with microencapsulated scents, is projected so that, during the preparation of the microcapsule emulsion in the phase of preparation of core material, water for the extraction of water soluble components is emulsified in a solution of essential oils and separated from oil after extraction. The essential oils or scents especially natural essential oil, synthetic scents or their mixtures, either pure scents or diluted with adequate solvents, such as phtalates, myristates adipates higher nonaromatic hydrocarbons are to be microencapsulated. It is essential that by means of water the water soluble components are extracted from the solution of essential oils in solvents. When initiating the wall the temperature is gradually increased from the value which corresponds to 50% temperature value of volatility of each essential oil or scent to the temperature which corresponds to approximately 90% temperature value of volatility of each essential oil or scent. When preparing the coating or impregnating mixture microencapsulated scent, binders, organic and or inorganic pigment sand fillers, anti-foaming agents and mediums for viscosity regulation are added, depending on the carrier. When coating the carrier, the coating in a form of suspension is applied either by scraper, air knife or cylinders; when impregnating woven or unwoven textile, paper cardboard or foil made of artificial material, it is transported through the impregnation basin, containing impregnating mixture. The possibilities of microencaplulation of scents based on modified or improved process according to the invention are if compared with the already known procedures (especially the Yugoslav patent P-1319/84) shown on the basis of examples, further on explained in detail. The obtained distributions according to particles size after emulsifying and curing are shown in figures 1 to 6. Microcapsule size was measured by Coulter Counter TA π after the phase of emulsifying and after curing phase. Before and after curing the emulsion was controlled with optical microscope in order to control the presence of possible microcapsule agglomerates. Microcapsule curing was evaluated by means of auxiliary microencapsulation where 3% leuco dye crystalviolet lacton (CVL) was added to the microcapsule core, containing a scent, and then microencapsulated according to the same process as with the scent only. Curing and consequently the diffusion and mechanical properties of microcapsules can be evaluated by curing test (according to method 1 further on described), and by smudge test (according to method 2 further on described). Microcapsule emulsion containing, in addition to scents, also microencapsulated leuco dye, can have viscosity adapted (100 to 150 mPa s) by dilution with water and can be applied to paper (50 g/m 2 ) by means of wire scraper. Applied coating can be dried (by ordinary hair drier) up to the value of 5 g/m 2 , by which the so called CB-sheet is obtained. After performing the curing test ace. to method 1, the CB-sheet, or its coated side, is coated with silica sol solution (Kisselsol 300 F, Bayer) and dried with hair drier. During drying the acid crystalizes and damages the microcapsule wall. Acting also as a developer of leuco dye, the acid reacts with it and develops a colour which can be measured by densitometer (measuring of optical density). Sometimes it is possible to make a comparison of colour developing between two sorts of microcapsules already with naked eyes. The intensity of colour image is inversely proportionate with the microcapsule wall strength but experiences show that microcapsules which develop more intensive image also possess higher diffusion. When performing the smudge test ace. to the method 2, it is possible to define the mechanical resistance of microcapsules, especially against shear stress, which plays an important role .when manipulating with coated carriers. CB-sheet in A4-size is placed on a smooth surface or table with coated side upwards. CF-sheet, (sheet with a colour developer) is placed on it so that both coated sides are in contact. CF-sheet is burdened with a weight of 0,5 kg (weight diameter 45 mm); the CF-sheet together with a weight is then pulled on CB sheet in the length of 200 mm. On the basis of colour intensity on the CF sheet it is possible to determine the mechanical resistance of the microcapsule walls. Rigidness or mechanical resistance of a wall is inversely proportionate with colour intensity. In the first example of process performing according to the invention peppermint essential oil was microencapsulated; 50 g of essential oil was dissolved in 150 g of i-propyl myristate. With help of dissolver mixer at 800-2000 rpm 20 g (15-25 g also possible) of deionized water was emulsified in this mixture. After 15 min. of mixing we poured the emulsion into separator and waited for emulsion to separate and then we split aside the water. Thus prepared oil was then again emulsified by dissolver mixer at 800-2000 rpm into 300 g of 5% solution of styrene maleinanhydride and 80 g of methylated melamin-formaldehyde precondensate having a pH value between 4.5 and 5.5 (preferably 5.5) and viscosity between 100 and 500 m Pa s (most preferred 200 Pa s). Emulsifying took 15 minutes at room temperature, in general, it takes as long as the desired particles size is obtained, i.e. between 3 and 10 micrometers. Then the emulsion was heated to 60-75°C (preferably 70°C) and kept at this temperature for 1 to 2 hours while continuously stirring. Further on we controlled the impermeability of microcapsules and then cooled the emulsion and stopped the reaction of curing by adding 5 g of 20% NaOH. The formaldehyde released through the reaction was eliminated by adding 10 g of 20% sodium bisulphite. In the comparative example the process according to the mentioned Yugoslav patent P-1319/84 was applied, without any changes but instead of leuco dyes the essential oil of peppermint was microencapsulated. In distinction from previously described we omitted the phase of treatment with water in this process. Microcapsules thus produced possessed substantially worse distribution of particles ace. to the size and poorer mechanical properties than those obtained by the process of the invention. In the second example of process performing according to the invention a mixture of essential oil of peppermint and citrus was used instead of the peppermint essential oil. The process characteristics and quantities corresponded to those quoted in relation with the first example of process performing according to the invention. In the third example of process performing according to the invention a mixture of eucalyptus and peppermint essential oils was used instead of the peppermint essential oil. The process characteristics and quantities corresponded to those quoted in relation with the first example of the process performing according to the invention. In the second and third example the process was the same as in the first example only that in the second comparative example a mixture of citrus and peppermint essential oil was used instead of peppermint essential oil and in the third example a mixture of eucalyptus and peppermint essential oils was used. Microcapsules which in addition to previously mentioned scents, contained 3% of leuco dye (CVL) as well, were also prepared. Figures from 1 to 6 show the obtained distribution of particle ace. to size after emulsifying and after curing, while mechanical properties of microcapsules measured according to the above described method 1 or method 2 (microcapsules containing 3% leuco dye "CVL") are shown in table 1 as follows. Figure 1 , as a result of the first example of process ace. to the invention, shows distribution of particles according to size where peppermint oil was used as a scent. In comparison, figure 2, as a result of the so far known process (P-1319/84), shows the distribution of particles according to size where peppermint oil was used as a scent as well. Figure 3, as a result of the second example of process performing according to the invention, shows distribution of particles ace. to size where a mixture of essential oils of peppermint and citrus was used as a scent. For the comparison reason and as a result of application of the already known process (P-1318/84), figure 4 shows distribution of particles according to size where a mixture of essential oils, as with the previous process - figure 3, was applied. As a result of the third example of process performing according to the invention, figure 5 shows distribution of particles according to the size. In this example a mixture of eucalyptus and peppermint essential oil was used. For comparison and as a result of application of the already known process (P-1319/84), figure 6 shows distribution of particles according to size. In this example the same mixture of essential oils was used as in example described under fig. 5. From the enclosed fig. 1 to 6 the distribution of particles size after emulsifying and curing are evident, while mechanical properties of microcapsules, measured by previously described method 1 or method 2 (microcapsules containing 3% leuco dye CVL) are shown in the following table 1. Example Curing Test Smudge Test Example 1 good curing poor smudge Comparison example 1 medium good curing strong smudge Example 2 good curing poor smudge Comparison example 2 poor curing very strong smudge Example 3 good curing poor smudge Comparison example 3 poor curing very strong smudge (Table 1) With the process of preparation of carriers, either by saturating or by coating with microencapsulated scents it is possible to obtain carriers, saturated or coated with microencapsulated scents where volatility of scent is prevented and the impact of environment to the scent or to its sensitive components is eliminated. With carriers thus obtained the need for impermeable, environmental unfriendly packaging is no longer required. As the scent release starts willingly, for instance during the application when microcapsule walls are damaged, under pressure, instead of unwilling permanent and therefore short-lasting effect of the scents, willing and therefore long-lasting release is possible. Thus the period of use of such carriers is prolonged, among other things also because the microcapsule wall protects the scent against diffusion where with diffusion actually very small quantities of scents are released. Further on, the carriers thus obtained can be additionally treated - in properly selected way - for example printed in the printing machine without losing scent.

Claims: P A T EN T C L A I M S 1. The process of preparation of carriers, impregnated or coated with microencapsulated scents, comprising the preparation of microcapsule emulsion, preparation of coating, and or saturating of carrier where preparation of the microcapsule emulsion comprises, in addition to the preparation of emulsion, also emulsifying of core material into a solution of wall material base, containing modifier, as well as the initiation of wall formation by raised temperature and/or by change of pH value and also finishing or interruption of the microencapsulation reaction by change of pH value and thus stopping the polymerization, characterized in that during the preparation of microcapsule emulsion in the phase of core material preparation water is emulsified into solution of essential oils and after the extraction separated from oil, wherein the demanded essential oils or demanded scents, especially natural essential oil, synthetic scents or the mixture of those, either pure scents or diluted with adequate solvents such as phtalates, myristates, adipates, higher nonaromatic hydrocarbons are microencapsulated and where water soluble components are extracted from the solution of essential oils in solvents by means of water; in addition to that, when initiating the wall, temperature is gradually increased from the value which corresponds to approximately 50% value of the volatility temperature of each essential oil or scent up to the temperature of which value corresponds approximately 90% value of volatility temperature of each essential oil or scent and in addition to that microencapsulated scent, binders, organic and/or organic pigments and filers, antifoaming agents and viscosity regulating mediums are added during the preparation of coating or to the impregnating mixture, depending on the carrier; and in addition to that when coating the carrier the coating in a form of suspension is applied by means of scraper, air knife or cylinders while for impregnation of carrier, either woven or non-woven textile, paper or foil of artificial material is transferred through the impregnation basin containing impregnating mixture. 2. The process according to the claim 1, characterized in that during the preparation of microcapsule emulsion in the phase of preparation of core material water for the extraction of water-soluble components is emulsified into a solution of essential oils and separated by means of gravitation in the separators after the extraction. 3. The process according to the claim 1 , characterized in that during the preparation of microcapsule emulsion in the phase of preparation of core material water for the extraction of water-soluble components is emulsified into a solution of essential oils and separated from the oil by means of cetrifuge, after the extraction.

Inventors: KNEZ EMIL, KUKOVIC MILENA, KNEZ, EMIL, KUKOVIC, MILENA
Applicants: AERO KEMICNA GRAFICNA IN PAPIR, KNEZ EMIL, KUKOVIC MILENA, AERO, KEMICNA, GRAFICNA IN PAPIRNA INDUSTRIJA,, KNEZ, EMIL, KUKOVIC, MILENA
Application year: 1995
Main classification: B01J13
IPC codes: B01J13, D06M15, D21H27