CS261957B1 - Core solvent of colorformers for direct copy paper production - Google Patents

Abstract

The solution relates to a core solvent of a colorant which is enclosed in microcapsules used in the production of direct-copy papers. By using a certain amount of polypropylene oil as an additional component of the core solvent, an increase in the emulsification rate and an increase in the durability of the resulting microcapsules is achieved.

Description

The invention relates to a core solvent of color-forming substances for the production of direct-copy papers, which is enclosed in microcapsules used in the production of direct-copy papers.

In the previously known systems of direct-copy papers of the chemical type, the fact is used that color-forming substances (for example, crystal violet lactone) react with the so-called color-developing substance (for example, the surface of acid-activated bentonite) to form an intensely colored compound. The solution of the color-forming substance in the core solvent is enclosed in microcapsules, which are applied to the underside of the paper sheet. The color-developing substance is applied to the top side of the following sheet. When writing, the microcapsules are broken by the pressure of the writing element and their contents flow out onto the surface of the following sheet, where the above-mentioned reaction occurs.

A description of these known systems is contained, for example, in US patent, document no. 4,093,378 or in GB patents no. 1,405,465 and 1,521,148. The basis for creating high-quality microcapsules is the preparation of a stable emulsion of the core solvent, which contains dissolved, in water.

The size of the emulsion droplets must be in the range of 1 — 3 μΐη. In the next stage, the droplets are coated with a polymer, which, when it reaches a sufficient layer thickness, forms a microcapsule.

After adding a binder, the direction is applied in the form of a coating on paper. The choice of core solvent plays an important role already in the emulsification phase of the preparation of microcapsules and affects their final quality, especially in terms of their impermeability and durability. With the core solvent systems used so far, the time required to create an emulsion with the desired particle size distribution is long and the preservation of the functional properties of the microcapsules during long-term storage is low.

The above disadvantages of existing systems are eliminated by the solution according to the invention, its essence is the use of a certain proportion (preferably 0.05 to 1.5 parts by weight) of polypropylene, with an average degree of polymerization of 7 to 12 and whose molecule contains on average 1 to

1.5 double bonds, into a core solvent consisting of 1 part by weight of a chlorinated n-alkane of C10 to C16 (20 to 50% by weight of Cl) or of 1 part by weight of a mixture of isopropyldiphenyl and diisopropyldiphenyl, where the content of diisopropyldiphenyl is 0.2 to 70% by weight. The addition of the said amount of polypropylene oil significantly improves the emulsifiability and durability of the core solvent and the microcapsules prepared therefrom.

The improvement of the properties of the core solvent is documented in the examples below, which do not, however, exhaust the possible combinations in which polypropylene oil favorably affects the ease of emulsification and durability of microcapsules.

Testing of emulsification ability is carried out by measuring the minimum emulsification time required to achieve an emulsion droplet size of less than 3 μΐη in a laboratory emulsifier under the same conditions.

Microcapsule durability testing is performed by monitoring the decline in the ability of microcapsules to produce a copy after their coating on paper has been subjected to accelerated heat aging at 120°C for 120 hours. It is given as the relative optical density of the copy compared to a copy made from unaged microcapsules. It is expressed in %.

Example 1

The colorant is dissolved in 1 part of chlorinated n-alkane and 0.4 parts of isoparaffinic solvent Sineroi 11 (product of Shell) are added. This solution is emulsified in a laboratory emulsifying device in an aqueous gelatin solution and the time Te required to achieve the size of the emulsion droplets < 3 μΐη is determined. Then, they are encapsulated in the usual way by the complex coacervation method. The properties of the resulting microcapsules and the emulsification time Te are given in the table. The colorant used is a mixture of crystal violet lactone and benzoyl linoleum methylene blue in a ratio of 3 : i. The concentration is 1.13 g/100 ml of core solvent.

Example 1 and 2

We proceed as in example 1, but instead of the isoparaffinic solvent, 0.4 parts of polypropylene oil (PPO) K-300 (product of Slovnaft) are added. Examples 3 to 6

We proceed as in example 2, but adding different amounts of polypropylene oil PPO K-300 (see table).

Example 7

Same as example 1, except that instead of chlorinated n-alkane we use a mixture of mono- and diisopropyldiphenyl (1:1).

TABLE

Example Core solvent composition (parts) Emulsification time (min) Decrease in optical density of a copy due to aging of microcapsules % PPO K-300 Isoparaffinic solvent Chlorinated n-alkane (40% Cl by weight) Mono- and diisopropyldiphenyl (1:1) 1 p. p. __ 0.4 1 .— 3.3 58 2 0.4 1 — 2.3 77 3 0.5 — 1 — 2.0 — 4 0.7 — 1 — 1.5 — 5 1 — 1 — 1.3 — 6 1.5 — 1 — 1.0 — 7 0.4 — — 1 2.4 78 8 pages. p. — — 1 3.8 81 From examples we see very favorable the effect of PPO content on increasing the emulsification rate and on

increasing the durability of the resulting microcapsules.

Claims (1)

Subject Coloring agent core solvent for the production of self-copy paper, consisting of 1 part by weight of chlorinated n-alkane of 10 to 16 carbon atoms (20 to 50% by weight of chlorine) or 1 part by weight of a mixture of said chlorinated n-alkane and isoparaffinic solvent The solvent in the mixture is less than 50% by weight, or 1 part by weight of a mixture of isopropyldiphenyl and diisopropyldiphenyl, wherein the content of diisopropyldiphenyl is 0.02 to 70% by weight, characterized in that it contains polypropylene having an average degree of polymerization of 7 to 12 in an amount of 0. , 05, up to 1.5 parts by weight.