JPH04253701A - Modified nitrocellulose - Google Patents

Abstract

PURPOSE:To obtain a modified nitrocellulose improved in adhesiveness, gloss, hiding power and coloration of vehicle by carboxylating nitrocellulose of a lowered molecular weight. CONSTITUTION:Nitrocellulose of a lowered molecular weight is obtained by subjecting nitrocellulose obtained by nitrating pulp to thermal hydrolysis, acid hydrolysis or alkali hydrolysis. This nitrocellulose is carboxylated by oxidation with an oxidizing agent to obtain a modified nitrocellulose having an average molecular weight of 20000 or below and a carboxyl content of 9mmol/ 100g of nitrocellulose.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to modified nitrocellulose, and more particularly to a new low-molecular nitrocellulose containing carboxyl groups. This substance is used in wood coatings, plastic coatings, printing inks, building materials coatings, metal coatings, paper coatings, leather coatings,
It is used as a film-forming element and dispersant in various coatings such as magnetic powder paints.

0002

BACKGROUND OF THE INVENTION Various nitrocelluloses specified in JIS-K6703 are known as film-forming elements for various coating agents and dispersants for various pigments. Coating compositions containing nitrocellulose generally have excellent drying properties and anti-blocking properties, but they have shortcomings in adhesion to substrates, gloss of coatings, hiding properties, and degree of vehicle coloration, and their applications are limited. It is only used in

JP-A-60-41086 describes that adhesion is improved when industrial nitrocellulose having an average degree of polymerization of 30 or less is used as a coating film-forming element in a plastic coating composition. However, this known technique of nitrocellulose has the disadvantage that the degree of coloring of the vehicle deteriorates as the degree of polymerization decreases.

[0004] As described in JP-A-63-14753, in a magnetic coating composition, as a dispersant for an oxide-based ferromagnetic material, a carboxyl group content of 2 in the molecule is used.
Although it is known that dispersion performance is improved when nitrocellulose is used in an amount of 100 g or more mmol/nitrocellulose, there is a problem particularly in terms of adhesion to plastic films, and there remains room for improvement.

It is known that in fields such as the paint and printing industries, the drying properties and viscosity of coating agents greatly affect productivity. Generally, it is known that if a coating agent contains a large amount of nitrocellulose, the dispersibility and drying properties of the pigment will be improved.However, there has been a contradiction in that the viscosity increases and the productivity decreases. Therefore, in conventional technology, the content of nitrocellulose was reduced to improve productivity, and the solid content of the coating agent was also reduced, making it impossible to obtain a thick coating film, resulting in poor gloss and hiding properties. There were some difficulties. Additionally, this technique requires a large amount of organic solvent, which poses environmental problems.

[0006] Conventional industrial nitrocellulose is
Since the lacquer itself is colored to some extent, it is rarely used as a clear lacquer, and there are points that need improvement. Therefore, there has been an increasing demand for nitrocellulose that has excellent adhesion, gloss, hiding properties, and vehicle coloration.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide nitrocellulose which has excellent adhesion, gloss, hiding properties and vehicle coloration.

[0008]

[Means for Solving the Problems] As a result of intensive studies, the present inventors have found that modified nitrocellulose, in which carboxyl groups are introduced into low molecular weight nitrocellulose, which has not conventionally existed as nitrocellulose, meets the above objectives. This discovery led to the present invention. That is, the present invention provides nitrocellulose with an average molecular weight of 20,000 or less,
The modified nitrocellulose has a carboxyl group content of 9 mmol/100 g of nitrocellulose or more.

It is essential that the modified nitrocellulose of the present invention has an average molecular weight of 20,000 or less, preferably 15,000 or less, and the carboxyl group content in the molecule is 9 mmol/100 g of nitrocellulose or more. It is essential that the amount is 12 mmol/100 g of nitrocellulose or more. Nitrocellulose outside this range is insufficient in terms of vehicle coloration, adhesion, gloss, and hiding properties. The average molecular weight here is
This is the value when the average molecular weight Mw was measured using TOSOH HLC8020 as a GPC (gel permeation chromatograph) device and GNHXL (2 columns) and G200OHXL (1 column) as columns. In addition, carboxyl group content refers to nitrocellulose 100
The amount of carboxyl groups contained per gram is expressed in mmol, and the measurement is performed as follows.

[0010] Accurately weigh 1 g of the dry sample, and
250 ml of 0.1 N hydrochloric acid is added to this, and the sample is left to stand for 2 hours to decalcify the sample. after that,
Filter the sample on a glass filter and wash with 1 liter of distilled water. Calcium hydroxide was added to 0.05 g calcium acetate/1 kg distilled water to adjust the pH to 10.2, and the mixture was placed in a 250 ml volumetric flask, and the nitrocellulose sample was added to it, shaken occasionally and left overnight. After that, 50 ml of supernatant
ml is placed in a beaker, ammonium chloride-ammonia buffer solution (NH4 Cl-NH4 OH) is added, and the mixture is titrated with a magnesium ethylenediaminetetraacetate solution using Eriochrome Black T as an indicator. In parallel with this, a blank test is performed, and the carboxyl group content is determined from these measurement results.

The modified nitrocellulose of the present invention is produced, for example, by the following method, but is not limited to these methods. The modified nitrocellulose of the present invention can be obtained by a manufacturing method by introducing carboxyl groups into nitrocellulose made into a low-molecular-weight nitrocellulose. That is, first, nitrified cotton obtained by nitrifying pulp is reduced in molecular weight by thermal decomposition or the like. Next, carboxyl groups are introduced by oxidizing the nitrified cotton, which has been reduced to a low molecular weight, using chlorate or the like.

The starting materials of the present invention include wood pulp,
In addition to natural cellulose such as cotton linter pulp, cotton linter, and ramie, regenerated cellulose such as rayon and cupra can also be used, but wood pulp and cotton linter pulp, which are the most common, are preferred in terms of ease of production. It is also possible to combine two or more of these as starting materials.

[0013] As the nitrification method, nitric acid/sulfuric acid, nitric acid/
Phosphoric acid, nitric acid/magnesium nitrate, nitric acid/acetic anhydride, fuming nitric acid, etc. can be used, and nitroglycol or nitroglycerin, which has been prepared in advance by esterifying the alcohol residue of cellulose to, for example, acetate, can be used. It is also possible to carry out transesterification with a nitroesterified product under the presence of a catalyst, but it is difficult to control the amount of nitrogen. Therefore, it is preferable to use nitric acid/sulfuric acid because it is easiest to adjust the amount of nitrogen.

Depolymerization methods include thermal hydrolysis using an autoclave, acid hydrolysis using dilute sulfuric acid, concentrated sulfuric acid, or concentrated hydrochloric acid, alkaline hydrolysis using sodium hydroxide, and decomposition using an air flow method using hydrochloric acid gas. Alternatively, it is also possible to mechanically pulverize into a low molecular weight using a vibration mill or the like. It is also possible to reduce the molecular weight by electron beam irradiation.

Carboxylation methods include common oxidizing agents such as chloric acids such as hypochlorous acid, chlorates such as sodium hypochlorite, chromic acids, chromates, dichromates, and peroxide. Hydrogen water etc. can be used. However, there are two types of oxidized cellulose, a reduced type and an acid type, and in order to introduce a reduced type carboxyl group, the above-mentioned oxidizing agent and pH must be appropriately selected.

[0016]Although cellulose cellulose may be used as the starting material as described above, in some cases it may also be produced from commercially available industrial nitrocellulose. The modified nitrocellulose of the present invention can be used as a composition in combination with a resin and a plasticizer. The resin used herein may be anything that can be used as a film-forming element in a coating agent. A coating film-forming element is one that essentially forms a coating film, excluding pigments and solvents (volatile components). Examples include epoxy resins, aminoalkyd resins, phenolic resins, maleic resins, urea resins, melamine resins, polyurethane resins, acrylic resins, styrene resins, vinyl chloride resins, vinyl acetate resins, vinyl butyral resins, cashew resins, alkyds. Examples include resins, chlorinated rubber, cyclized rubber, chlorinated polypropylene resins, ethylene vinyl acetate copolymer resins, and mixtures of two or more of these.

Examples of plasticizers include phthalic acid esters such as dibutyl phthalate and dioctyl phthalate, phosphoric acid esters such as tricresyl phosphate and trichloroethyl phosphate, sebacic acid esters, adipic acid esters, citric acid esters, and these two. Examples include mixtures of more than one type. These resins and plasticizers can be used selectively depending on the purpose. Additionally, additives such as wear resistance improvers, antistatic agents, and weather resistance improvers can also be used. The above composition containing the modified nitrocellulose of the present invention is
It can be coated or printed on any substrate including plastic, metal, paper, cloth, wood, and leather.

[0018]

[Examples] The present invention will be explained below with reference to Examples. The evaluation and measurement methods for the coating film and vehicle containing the modified nitrocellulose of the present invention were as follows. (Vehicle coloration measurement test) A vehicle containing nitrocellulose was placed in a colorimetric tube for Hazen Number measurement shown in Fig. 1 up to the height of the marked line, and the stopper was closed.
Observe from the liquid surface to the bottom under forward light from the north window ray or similar light, and sequentially measure the Hazen standard solution a)
The number of the standard solution that was colored to the same extent as the sample solution was found by color comparison, and the degree of coloring was determined by the Hazen Number (HN
).

Note a) Preparation of Hazen Number standard solution Platinum potassium chloride (special grade reagent) 1,246 g and cobalt chloride (JIS K8129: special grade reagent) 1,00
Weigh out 0 g, put it into a 1000 ml volumetric flask, and add about 500 ml of distilled water to dissolve it. Then hydrochloric acid (JIS
Add 100 ml of K8180 (special grade reagent) and then add distilled water to make exactly 1000 ml. This solution was
azen Standard No. 500, and from this, Hazen standard solution No. Accurately measure the value (ml) corresponding to , put it into a 500 ml volumetric flask, and add distilled water up to the marked line. In this way, the required H
Prepare an azen standard solution, fill each colorimetric tube as shown in Figure 1 up to the height of the marked line, stopper it, and harden it with wax. (Adhesion test) After wiping the coating agent containing nitrocellulose with isopropyl alcohol,
Wet the commercially available PET film annealed for 2 hours at
= 20°C using a 25μ Baker applicator, 6
After coating in an atmosphere of 5% RH and drying for two days in the same atmosphere, an adhesion test was conducted in the manner described below.

Adhesion test: 2 days, 20°C, 65%RH
A cellophane tape (Nichiban No. 405) was placed on the air-dried paint film in an atmosphere of 100 ml, and after pressing with the thumb 5 times, it was rapidly peeled off and the peeling state of the coated surface was evaluated using the following criteria. XX...All peeled off. x: 80% or more peeled off.

Δ: 50% or more peeled off. ○: 20% or more peeled off. ◎ ...0 to 20% or more peeled off. ◎◎・・・No peeling at all. (Gloss Test) A coating agent containing nitrocellulose was applied onto a polished glass plate with a smooth surface using a Baker applicator with a WFT of 76μ. Then, after pre-drying at room temperature for 30 minutes and further drying at 80°C for 24 hours, it was measured at 60°/200° using a digital variable angle gloss meter (Suga Test Instruments Co., Ltd.).
The 60° specular gloss was measured. Note that the measurement was performed with the standard blackboard as a reference set at 91.5. (Occupancy test) The viscosity of the coating agent containing nitrocellulose was adjusted to 15 seconds (Ford cup/20°C) using the same thinner as in the coating agent, and this was applied using a Baker applicator with WFT = 254μ. 20℃, 65%RH
It was dried for 2 days in an atmosphere of Using a color difference meter (Suga Test Instruments Co., Ltd.), the color difference ΔE between the white and black parts of the base of the opacity test paper was measured for this coating film.

[0022]

[Example 1] Nitrocellulose HIG1/16 [manufactured by Asahi Kasei Kogyo Co., Ltd., containing 30% isopropyl alcohol] was poured into 10 times the amount of water, thoroughly stirred, and then dehydrated using a centrifuge. After repeating this operation 5 times, 5 times the amount of water and 1.5 times the amount of 24% sodium hydroxide aqueous solution were added and heated at 50° C. for 60 minutes. Next, this reaction solution was discharged, and the nitrocellulose was washed once with 10 times the amount of water, then 5 times the amount of water was added, the pH was controlled to 9, and the nitrocellulose was washed once with 10 times the amount of water.
Double the amount of 12% sodium hypochlorite was added and heated at 50°C for 60 minutes to obtain modified nitrocellulose. Table 3 shows the measurement results of the average molecular weight and carboxyl group content of the obtained nitrocellulose.

In order to observe the degree of coloration of this nitrocellulose, a vehicle containing no pigment was prepared according to the formulation shown in Table 1. In addition, coating agents for plastics were prepared according to the formulations shown in Table 2 in order to evaluate hiding properties, gloss, and adhesion. These vehicles and coating agents were tested for degree of coloration, adhesion, gloss and hiding properties, and the results are shown in Table 3.

[0024]

[Comparative Examples 1 to 7] Nitrocellulose HIG1/16 (Comparative Example 1), SL-1 (Comparative Example 2), HIK1/8 (Comparative Example 3), HIG1/2 (Comparative Example 4), HIG2 (Comparative Example 5) ), LIG1/8 (Comparative Example 6), and LIG1/2 (Comparative Example 7) were used to prepare a vehicle according to the formulation shown in Table 1 and a composition according to the formulation shown in Table 2, and the degree of vehicle coloration, adhesion, gloss and A concealability test was conducted. The results are shown in Table 3.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

Example 2 Modified nitrocellulose was obtained in the same manner as in Example 1, except that the amount of 24% sodium hydroxide added was 1/2 and the amount of 12% sodium hypochlorite was doubled. The average molecular weight and carboxyl group weight of the nitrocellulose,
Table 4 also shows the measurement results of vehicle coloration, adhesion, gloss, and opacity tests conducted according to Example 1.

[0029]

[Example 3] Modified nitrocellulose was prepared in the same manner as in Example 1, except that 24% sodium hydroxide was used in 3/4 times the amount and 12% sodium hypochlorite was used as the oxidizing agent in 1.5 times the amount. Obtained. Table 4 shows the average molecular weight and carboxyl group weight of the nitrocellulose, as well as the measurement results of vehicle coloration, adhesion, gloss and opacity tests conducted according to Example 1.

[0030]

[Comparative Example 8] The starting material was nitrocellulose HIG1/8
[Manufactured by Asahi Kasei Industries, Ltd., isopropyl alcohol 30%
Modified nitrocellulose was obtained in the same manner as in Example 2 except that the modified nitrocellulose was contained. Table 4 shows the average molecular weight and carboxyl group weight of the nitrocellulose, as well as the measurement results of vehicle coloration, adhesion, gloss and opacity tests conducted according to Example 1.

[0031]

[Comparative Example 9] Modified nitrocellulose was obtained in the same manner as in Example 3, except that 12% sodium hypochlorite was used in 1.2 times the amount. Table 4 shows the average molecular weight and carboxyl group weight of the nitrocellulose, as well as the measurement results of vehicle coloration, adhesion, gloss and hiding properties tests conducted according to Example 1.

[0032]

[Table 4]

[0033]

Example 4 Printing ink compositions shown in Table 5 were prepared using the modified nitrocellulose of Example 1 and the nitrocellulose of Comparative Examples 1 to 7. The degree of coloring of this ink composition was measured. Next, 21.8 g of titanium dioxide (manufactured by Ishihara Sangyo Co., Ltd., TIPAQUE R-820) was added to the composition to prepare a printing ink, and a concealment test was conducted in the same manner as in Example 1. In addition, this printing ink was applied onto a commercially processed polypropylene film using a bar coater; Rod No.
．． 18 (manufactured by R.D. Specialties) at 20℃, 6
5%R. H. It was applied under the same atmosphere and dried for 2 days under the same atmosphere, and then an adhesion test and a gloss test were conducted using this. Table 6 shows the results of the degree of coloration, adhesion, gloss and opacity tests.

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

Effects of the Invention The modified nitrocellulose of the present invention is a hitherto unknown ultra-low molecular carboxylated nitrocellulose, and because of its low molecular weight, it dissolves quickly in solvents, making it easier to work with when creating paints. and can bring about superior productivity results. In addition, because it has a carboxyl group in its molecule, it has stronger chemical affinity than conventional nitrocellulose, and has excellent pigment dispersibility and metal adhesion.

[0037] When the modified nitrocellulose of the present invention is dissolved in an organic solvent, the nitrocellulose content can be increased while maintaining the same viscosity compared to conventional nitrocellulose, that is, high solidity can be achieved. be. This has the characteristic that, for example, it is possible to improve the dispersibility of pigments, etc. in paints, and it also reduces the amount of organic solvents used by making paints more solid, which greatly reduces environmental problems. can contribute.

Furthermore, since the product of the present invention provides an excellent degree of vehicle coloring, it can be applied to clear lacquers and coatings based on white backgrounds, which have not been used much in the past, and drying properties and workability are particularly important. Excellent results can be expected in the fields of interest.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a colorimetric tube used to measure the degree of coloration of a vehicle containing modified nitrocellulose of the present invention.

[Explanation of symbols]

1 Main body 2 Lid 3 Marked line 4 Grinding part

Claims (1)

[Claims] Claim 1: Nitrocellulose having an average molecular weight of 20,000 or less and a carboxyl group content of 9 mmo
A modified nitrocellulose characterized by having a content of 100 g or more per l/nitrocellulose.