JPH0380107A - Lipophilic modified basic calcium carbonate and production thereof - Google Patents

Abstract

PURPOSE:To obtain modified calcium carbonate having a permanently lipophilic surface and useful as a general-purpose white filler for plastics by coating the surface of flat platy submicroscopic basic calcium carbonate with higher fatty acid. CONSTITUTION:A coating layer of higher fatty acid having a straight chain of satd. hydrocarbon, e.g. lauric acid or higher fatty acid having a straight chain of at least 8C satd. hydrocarbon per one carbon-carbon double bond, e.g. oleic acid is formed on the surface of basic calcium carbonate composed of flat platy particles of 0.1-1.0mum particle size. The coating layer has an area equal to or larger than the surface area of the basic calciurn carbonate measured by a nitrogen adsorption method (BET method).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to basic calcium carbonate, and more particularly, the present invention is made of tabular Zabumicron particles suitable as a general-purpose white leading agent for plastics, and has a permanent parent This invention relates to basic calcium carbonate modified to have an oily surface and a method for producing the same.

[Conventional technology]

Powders of various inorganic compounds and minerals have been used as general-purpose fillers in order to impart desirable physical properties to plastic composites and to obtain economic effects. The typical examples are light calcium carbonate,
These include heavy calcium carbonate, talc, and kaolin clay. In order to improve the affinity of these inorganic compounds and mineral powders for polymer matrices, surface modification with various organic compounds has also been carried out. However, these conventional inorganic fillers have some drawbacks in their use. For example, among light calcium carbonate, ordinary products have a particle size of 1 to 2 μm or more, and because the particle size is relatively large, a composite filled with this is subject to irreversible stress due to tension or bending. It has the disadvantage of causing whitening and impairing the color tone of the composite. Colloidal calcium carbonate, which consists of submicron particles, is available in various particle size grades between 0.03 μm and 0.3 μm, but the particle shape of these colloidal calcium carbonates is usually cubic. These are nearly rhombohedral calcite crystals, and the dimensional stability of plastic compounds filled with them is not sufficient during processing and molding. Heavy calcium carbonate is crystalline limestone (
This is a mechanically crushed product of calzite), and grades with various particle size distributions are provided by classifying the crushed product during the manufacturing process, but the particle size is coarse and the particle shape is irregular block-like. However, it has drawbacks similar to ordinary light calcium carbonate products. Furthermore, these particles were far from the flat plate shape that is considered to be the ideal particle shape for plastic fillers. Talc and kaolin are clay minerals with a layered structure, and products consisting of submicron-level tabular grains with ideal particle shapes and shapes are supplied.
It is contaminated to a greater or lesser extent by natural soil colorants such as humus, iron and titanium oxides, and the production of highly white raw minerals such as calcium carbonate, which is close to pure white, is limited in some areas. Currently, there is generally no economical process to adequately remove these colored contaminants. There is a strong need to supply an ideal general-purpose filler with high whiteness and consisting of submicron particle size and tabular particle shape, such as talc and carrion. For example, published by the Gypsum and Lime Society,
"Gypsum and Lime" Magazine No. 198 (September 1985) Special Issue on Inorganic Fillers, pages 66 to 74, Yasuo Tsuruta, "Characteristics of Inorganic Fillers and Their Combined Effects" A request for appearance is stated. Furthermore, there is a potential demand for low specific gravity fillers as inorganic fillers for plastics in general to contribute to the weight reduction and volumetric cost reduction effect of composites.

A technology has already been developed to produce basic calcium carbonate consisting of submicron-sized tabular particles by carbonating milk of lime by introducing carbon dioxide gas under controlled conditions (Hideo Yamada, Naomichi Hara, Gypsum and lime, No. 198.
Pages 130-140.

1985, Hideo Yamada, Naomichi Hara, Published 60-71523
). This product has a specific gravity of 2.3 to 2.4 and calcium carbonate (2.
, 7), talc (2, 8), and carrion (2, 6) are preferable, but when this product is filtered and dehydrated from the production reaction system and dried, large secondary coagulated particles are formed due to strong interparticle coagulation. was formed and was extremely poorly dispersed in the polymer matrix and did not function as a filler at all. In other words, in order to turn basic calcium carbonate into a material as a filler for plastics, it is necessary to weaken its strong interparticle coagulation force and to hydrophobize the strong hydrophilicity of the particle surface due to the hydroxyl group, which is a basic group. It is necessary to convert it to lipophilicity and improve its wetting and dispersibility in organic matrices.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a lipophilic modified basic calcium carbonate which is preferable as a general-purpose white filler for plastics and solves the problems in the prior art.

[Means for Solving the Problems] As mentioned above, the present invention is based on flat or thin plate-like submicron (0.1 μm to 1 μm) particles such as talc and kaolin, which are preferable as general-purpose fillers for plastics. The particle surface is intended to provide basic calcium carbonate whose particle surface is permanently modified to be lipophilic.

By introducing milk of lime under controlled conditions and a predetermined ratio of carbon dioxide gas to calcium hydroxide,
A suspension containing cardhouse-shaped aggregates consisting of tabular basic calcium carbonate secondary particles having a particle size set in the range of .mu.m or more and less than 1 .mu.m is obtained. From this suspension, filtration,
Basic calcium carbonate powder obtained through normal processes such as dehydration, drying, and pulverization becomes secondary particles of aggregates with poor affinity and poor dispersibility for the polymer matrix, and the fine particle nature of the primary particles is completely eliminated. Not demonstrated. In order to make crystal useful as a general-purpose filler for plastics, the first step is to
In addition to weakening the strong cohesive force between primary particles, polymers,
In order to increase compatibility with organic matrices such as plasticizers and other organic liquids, conversion of particle surface hydrophilicity to permanent particle surface lipophilicity must be achieved. Furthermore, it is desirable to generate molecular entanglements through interaction in the molecular dimension at the interface between the particle surface substance and the matrix in order to prevent the generation of pores at the particle-matrix interface.

Now, the present inventors succeeded in solving the above-mentioned problem by forming a coating layer of a certain kind of preferable organic compound on the surface of the basic calcium carbonate particles in a basic calcium carbonate production system. did. The organic compound has a functional group in its molecular structure that permanently bonds with the surface of the basic calcium carbonate particles, and on the other hand, the organic compound forms a coating layer on the particle surface and forms a matrix at the interface. Preferred organic compounds are typically dual-functional ones that have lipophilic groups with dimensions that create opportunities for entanglement with polymer molecules, such as higher fatty acids, preferably saturated fatty acids with a low degree of unsaturation. A fatty acid having a hydrocarbon chain, generally speaking for achieving the present invention, selected from higher fatty acids having a straight hydrocarbon chain consisting of at least 8 carbon atoms per carboxyl group or carbon double bond. be able to.

For example, Lauric acid C11H23COOH Myristic acid C13H27COOH Valmitic acid C15H31COOH Stearic acid C17H35COOH Arachic acid Ct 9 Hs 9 COOH Behenic acid C
21■43COOH Oleic acid C3H17CH- CHC7H14COOH Erucic acid C3H17CH- CHC11H22COOH It may be a single fatty acid such as C3H17CH- CHC11H22COOH, or a natural oil or fat hydrolyzate containing these fatty acids as a main component, or a hydrogenated product thereof.

In order to form an adsorption layer on the surface of basic calcium carbonate particles by adding it to a basic calcium carbonate suspension, a fatty acid selected from the above is dissolved in a hot aqueous solution containing an amount of alkali hydroxide in an amount equivalent to neutralization. This can be achieved by converting it into an ionic state and adding it to a basic calcium carbonate suspension.

Next, the amount of fatty acid added necessary to convert the basic calcium carbonate particle surface to sufficient lipophilicity is, for example, BE
Based on the specific surface area of the basic calcium carbonate obtained from the T nitrogen adsorption method, the area occupied by a monolayer per molecule of fat M, and the molecular weight, the particle different area was determined as a sufficient area to be saturated with the t1+ molecular film of the fatty acid. It can be found by calculation. An example of this subtraction is shown below.

Basic calcium carbonate specific surface area 14TIi, / 'j
(T, ) Occupied area of one molecule of lauric acid 23A2
” (1 [) Molecular weight of lauric acid 200
, (III), basic calcium carbonate 100
The amount of lauric acid required per gram is 2.057 (calculation: *) "New Edition Fatty Acid Chemistry" edited by Megumi Inaba-2 Hirano (first published on September 5, 1980; Yukitsunabo), p. 58.

According to Table 343.

Now, when a hot aqueous solution of fatty acid j' lucali is added to a basic calcium carbonate suspension, the fatty acid anion, which has become an anion, is firmly fixed by electrostatic bonding to the positively charged center on the surface of the salt star lucium carbonate particle. The hydrocarbon chains, which are new bending groups, are oriented outward to achieve permanent new bending properties. Since this reaction proceeds in a short time, it is desirable to continue to vigorously stir the basic calcium carbonate suspension with a high-shear mixer before adding the hot aqueous solution of fatty acid alkali.

The suspension is then filtered and dehydrated to dry the 'IJta//-4-, and then ground through a hammer mill to form a powder. It is clear that the product has been modified to be lipophilic because even when the powder is added to water and stirred, it does not get wet at all and floats on the water surface.

〔Example〕

Example 1 Production of lipophilic modified basic lucium carbonate Specific surface area is 13.8'n1.7g, average particle diameter is 0.3
10% of nearly uniform tabular basic calcium carbonate of om
Pour 10 kg of water suspension into a 30-blade polyethylene reaction tank, and use a disc-type impeller mill to adjust the pH to 2.0 O OrpH.
Stir with +. Separately, 25 g of coconut fatty acid (neutralization value 265, iodine value 8) was added to 250 g of a hot aqueous solution containing 4.625 g of sodium hydroxide and completely dissolved. This hot aqueous solution of sodium coconut fatty acid was added to the basic calcium carbonate suspension, stirred for 15 minutes, and then dehydrated using a filter press. The obtained press cake was dried in a hot air dryer at 60°C and then ground in a hammer mill.

The product sample obtained above was dried in a desiccator for 24 hours,
Accurately weigh 10g of the sample, put it into a 300ml separatory funnel, add ethyl alcohol dropwise to the sample to moisten it, add 1:1 hydrochloric acid to decompose it, and after the carbon dioxide gas has stopped bubbling, add ethyl ether to liberate it. Fatty acids were extracted. Extract operation 3
The result of repeating this process several times was to combine the extracted acids and evaporate the ether to obtain a fatty acid concentration of 2.27% (the amount required to form a monomolecular film in this example was 2.0%).

Example 2 Soft vinyl chloride resin formulation Lipophilic modified basic calcium carbonate with coconut fatty acid produced in the same manner as in Example 1 was blended into a soft vinyl chloride resin, and the compounding properties were evaluated.

For comparison, basic calcium carbonate without fatty acid treatment was also tested at the same time.

Compounded polyvinyl chloride resin (SL) dioctyl phthalate tri-based lead stearate filler sample Compounding test Test conditions Dry-up test: Set temperature 100°C; Planetary mill rotation speed 70 rpm Kneading test: Set temperature 160°C; Roller 5 minutes at 25 rpm, then 50 rpm including 60 g Mixer rotation speed Compound weight part 100 (400 g) 5 o (200 g) 5 (20 g) 1 (4 g) 3100 (400 Kisa-no 3 Extrusion test: Set temperature 140 ° C ~ Intermediate 150℃~160℃~
Exit: 160°C, screw rotation speed: 30 rpms, die head: 50 x 0.5 m, ribbon type 4. All of the obtained extruded test pieces turned pink, with Sample I being more strongly colored than Sample II. When the test piece was observed using a 6x magnifying glass, it was observed that basic calcium carbonate was dispersed as coarse secondary coagulated particles in a satin-like pattern.

Formulation and test conditions: Same as Experiment 1 5 7 6 As is clear from Tests 1 and 2 above, lipophilic modified basic calcium carbonate obtained by surface treatment with a sufficient amount of fatty acid (
Test ■1 The product of the present invention) has a short dry-up time,
It is clear that it shows excellent kneading properties and extrudability, and is excellent in processability.

Sample ■ Compound extrusion test piece, which is a product of the present invention, has no discoloration.
Since the dispersion state is good and stress whitening is not observed even when the test piece is bent, the ability to form molecular entanglements with the polymer matrix at the particle interface is also good. This is clear compared to the fact that stress whitening occurs easily.

〔Effect of the invention〕

The present invention is configured as described above.

The lipophilic modified basic calcium carbonate obtained by achieving the present invention exhibits good dispersibility in plastic matrices such as soft vinyl chloride resin,
Excellent compatibility between the surface of the dispersed particles and the matrix,
It has excellent compounding and moldability in plastic molding processes, and can be provided as a general-purpose white filler for plastics. In addition, basic calcium carbonate itself, calcium carbonate (calcite, aragonite),
Since the specific gravity is lower than that of conventional general-purpose white fillers such as talc and kaolin, it is possible to provide a light plastic composite by filling the product of the present invention.

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Claims (1)

[Scope of Claims] 1. The particle surface of basic calcium carbonate consisting of tabular particles with a particle size of 0.1 μm or more and 1.0 μm or less is a monovalent higher fatty acid having a saturated hydrocarbon linear chain or carbon A lipophilic modified basic calcium carbonate characterized by forming a coating layer saturated with an adsorption layer of a monovalent higher fatty acid having a straight saturated hydrocarbon chain having at least 8 carbon atoms per double bond. . 2. The parent according to claim 1, wherein the coating layer is a higher fatty acid coating layer having an occupied area at least equal to the surface area of basic calcium carbonate measured by a nitrogen adsorption method (BET method). Oil-based modified basic calcium carbonate. 3. To an aqueous suspension of basic calcium carbonate consisting of tabular particles with a particle size of 0.1 μm or more and 1.0 μm or less, add a monovalent higher fatty acid having a saturated hydrocarbon straight chain or per carbon double bond. An aqueous solution of an alkali salt of a monovalent higher fatty acid having a straight saturated hydrocarbon chain consisting of at least 8 carbon atoms is added in an amount such that the area occupied by the higher fatty acid is at least equal to the surface area of the basic calcium carbonate. The lipophilic modified base is characterized in that the particle surface is permanently converted to lipophilic by adding it to form a coating layer of the higher fatty acid on the particle surface, followed by filtration, dehydration, drying, and pulverization. Method for producing calcium carbonate.