CN114450334B

CN114450334B - Cellulose acetate particle

Info

Publication number: CN114450334B
Application number: CN202080067146.1A
Authority: CN
Inventors: 水野将宏; 小山田直广
Original assignee: Daicel Corp
Current assignee: Daicel Corp
Priority date: 2020-01-16
Filing date: 2020-01-16
Publication date: 2024-02-06
Anticipated expiration: 2040-01-16
Also published as: TWI839566B; WO2021144914A1; CN114450334A; TW202128776A

Abstract

The purpose of the present disclosure is to provide cellulose acetate particles that can give a molded body of cellulose acetate having good strength and high transparency. A cellulose acetate particle comprising cellulose acetate and a plasticizer, wherein the melt flow rate is more than 1.0g/10min and less than 2.8g/10min, the total sulfuric acid is 20ppm or more and 170ppm or less, and the calcium concentration is 22ppm or more and 37ppm or less, the degree of substitution of acetyl groups of the cellulose acetate is 2.2 or more and 2.6 or less, and the content of the plasticizer is 30 parts by weight or more and 44 parts by weight or less relative to 100 parts by weight of the cellulose acetate.

Description

Cellulose acetate particle

Technical Field

The present disclosure relates to a cellulose acetate particle.

Background

Cellulose acetate is one of organic acid esters of cellulose, which is a cellulose derivative, and its use is widely used in various fields such as clothing fibers, cigarette filters, plastics, films, paints, pharmaceuticals, foods, cosmetics, and architectural uses, and is an industrially important substance in which the production amount of cellulose derivatives is large.

As a typical industrial process for producing cellulose acetate, there is a so-called acetic acid process in which acetic anhydride is used as an acetylating agent, acetic acid is used as a diluent, and sulfuric acid is used as a catalyst. The basic steps of the acetic acid method include the following steps (patent document 1 and non-patent document 1): (1) A pretreatment step of dissociating and/or crushing a pulp raw material (dissolving pulp) having a high alpha-cellulose content, and then spraying and mixing acetic acid; (2) An acetylation step of subjecting the pretreated pulp of (1) to an acetylation reaction using a mixed acid composed of acetic anhydride, acetic acid and an acetylation catalyst (for example, sulfuric acid); (3) A curing step of hydrolyzing cellulose acetate to obtain cellulose acetate having a desired degree of acetylation; and (4) a post-treatment step of separating, purifying, stabilizing and drying the cellulose acetate precipitate after the completion of the hydrolysis reaction from the reaction solution.

The cellulose acetate produced by the above-described method is used as a raw material, and the color of the fiber, film or plastic obtained by molding is often colored in a yellow color, and even if other properties are satisfied, there is a disadvantage in appearance, which results in a decrease in commercial value.

Therefore, in order to reduce the yellowness of cellulose acetate, secondary treatments such as adding a white pigment, a fluorescent whitening agent, a bleaching agent, and an antioxidant during molding are generally performed. For example, it is common to add pigments such as titanium dioxide to cigarette filters. This solution is not essential, and its effect is limited.

On the other hand, attempts have also been made to directly obtain cellulose acetate having excellent hue by reducing the yellowness. For example, it is disclosed that hemicellulose components in wood pulp are responsible for yellowness (non-patent documents 2 and 3): cellulose acetate excellent in transparency can be obtained by adding an organic solvent at the time of producing cellulose acetate (patent document 2) or by once dissolving cellulose diacetate in a solvent having good solubility and then recovering it (patent document 3).

In recent years, the addition of a light color to a cellulose acetate molded article has been popular, and a fashion with higher transparency has been pursued, so that a cellulose acetate molded article having a more excellent hue and excellent transparency, which solves the problem of yellowness at a higher level, has been demanded.

The cellulose acetate molded article is produced mainly by: first, cellulose acetate (sheet), a plasticizer, and optional additives as needed are melt-kneaded to prepare cellulose acetate particles (a granular composition containing cellulose acetate and a plasticizer), and further subjected to molding processing such as a melt extrusion method.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 56-059801

Patent document 2: japanese patent laid-open No. H06-157601

Patent document 3: japanese patent laid-open No. H06-157602

Non-patent literature

Non-patent document 1: macromol. Symp.2004,208,49-60

Non-patent document 2: J.D.Wilson, R.S.Tabke Tappi,57,77 (1974)

Non-patent document 3: F.L.Wells, W.C.Shattner, A.Walker Tappi,46,581 (1963)

Disclosure of Invention

Problems to be solved by the invention

If the transparency of the cellulose acetate particle is insufficient, a molded article having high transparency cannot be obtained. However, even when cellulose acetate (flakes) having a low yellow hue and an excellent hue is used, cellulose acetate particles having a low yellow hue and an excellent hue are not necessarily obtained, and it is difficult to produce cellulose acetate particles having high transparency. Further, in various applications such as fiber materials for clothing, frames for glasses and sunglasses, and building materials, strength of molded articles is required, but it is difficult to obtain molded articles of cellulose acetate having good strength and high transparency.

The purpose of the present disclosure is to provide cellulose acetate particles that can give a molded body of cellulose acetate having good strength and high transparency.

Technical proposal

The present disclosure relates to a cellulose acetate particle containing cellulose acetate and a plasticizer, the melt flow rate exceeding 1.0g/10min and less than 2.8g/10min, the total sulfuric acid being 20ppm or more and 170ppm or less, and the calcium concentration being 22ppm or more and 37ppm or less, the degree of substitution of acetyl groups of the cellulose acetate being 2.2 or more and 2.6 or less, the content of the plasticizer being 30 parts by weight or more and 44 parts by weight or less relative to 100 parts by weight of the cellulose acetate.

Preferably, in the cellulose acetate particle, the plasticizer comprises at least one selected from the group consisting of a glyceride-based plasticizer and a phthalic acid-based plasticizer.

Preferably, in the cellulose acetate particle, YI (yellow index) value is 20 or less.

Preferably, in the cellulose acetate particle, the melt flow rate is 1.2g/10min or more and 2.3g/10min or less.

Effects of the invention

According to the cellulose acetate particle of the present disclosure, a molded body of cellulose acetate having good strength and high transparency can be obtained.

Detailed Description

[ cellulose acetate particles ]

An example of the preferred embodiment will be specifically described below. The cellulose acetate particle of the present disclosure contains cellulose acetate having an acetyl substitution degree of 2.2 to 2.6 and a plasticizer, and a melt flow rate of more than 1.0g/10min and less than 2.8g/10min, a total sulfuric acid of 20ppm to 170ppm, and a calcium concentration of 22ppm to 37ppm, and a content of the plasticizer is 30 parts by weight to 44 parts by weight based on 100 parts by weight of the cellulose acetate.

The particles in the cellulose acetate particles are particles obtained by melt-kneading cellulose acetate, a plasticizer, and optionally additives, etc., to form a particulate shape. The method of melt kneading is not particularly limited, but there may be mentioned a method of forming strands by a melt extrusion method using a single screw or twin screw extruder, and cutting them into pellets, and the like.

(melt flow Rate (MFR))

The Melt Flow Rate (MFR) of the cellulose acetate particles of the present disclosure exceeds 1.0g/10min and is less than 2.8g/10min. The MFR is preferably 1.2g/10min or more, more preferably 1.5g/10min or more, and still more preferably 2.0g/10min or more. Further, the MFR is preferably 2.5g/10min or less, more preferably 2.3g/10min or less.

When the MFR is 1.0g/10min or less, the hue of the obtained molded article is poor. In addition, in the case of attempting to obtain a molded article, the fluidity of the molten cellulose acetate particles is too high, and the possibility of leakage from the mold becomes high. On the other hand, when the MFR is 2.8g/10min or more, the mechanical strength is poor, in particular, the tensile properties and bending properties, or the toughness is poor. In addition, in the case of attempting to obtain a molded article, fluidity of the molten cellulose acetate particles is low, and surface smoothness of the obtained molded article may be deteriorated.

The MFR was determined in accordance with JIS-K7210 at 200℃under a load of 2.16 kg.

(Total sulfuric acid)

The cellulose acetate particle of the present disclosure has a total sulfuric acid of 20ppm to 170 ppm. The total sulfuric acid may be 30ppm or more and may be 50ppm or more. The total sulfuric acid may be 150ppm or less, 120ppm or less, 100ppm or less, or 80ppm or less.

By the total sulfuric acid being in the above range, a molded body of cellulose acetate having good strength and high transparency can be obtained from the cellulose acetate particle of the present disclosure. If the total sulfuric acid exceeds 170ppm, the hue of the obtained molded article is poor.

The total sulfuric acid is the amount of sulfuric acid in 1g of the cellulose acetate particle in an absolute dry state, and can be measured using dry cellulose acetate particle coulometry.

(calcium concentration)

The calcium concentration of the cellulose acetate particle of the present disclosure is 22ppm or more and 37ppm or less. The calcium concentration may be 23ppm or more, may be 26ppm or more, and may be 28ppm or more. The calcium concentration may be 34ppm or less, 33ppm or less, or 31ppm or less.

By the calcium concentration falling within the above range, a molded body of cellulose acetate having good strength and high transparency can be obtained from the cellulose acetate particle of the present disclosure. If the calcium concentration is less than 22ppm or exceeds 37ppm, the hue of the obtained molded article is poor.

(magnesium concentration)

The magnesium concentration of the cellulose acetate particle of the present disclosure may be 1ppm or more and 50ppm or less, and may be 1ppm or more and 20ppm or less.

(calcium and magnesium concentration)

The cellulose acetate particle of the present disclosure may have a combined concentration of calcium and magnesium of 0.5 to 3. Mu. Mol/g, and may have a combined concentration of 0.9 to 2.0. Mu. Mol/g.

The calcium concentration (or magnesium concentration) of the cellulose acetate particle can be determined by the following method. 3.0g of an undried sample was measured in a crucible, carbonized by an electric heater, and then ashed in an electric furnace at 750℃or higher and 850℃for about 2 hours. After cooling for about 30 minutes, 25mL of a 0.07 wt% hydrochloric acid solution was added, and the mixture was heated and dissolved at 220 to 230 ℃. After cooling, the dissolved solution was fixed to 200mL with distilled water, and the absorbance was measured with an atomic absorption spectrometer together with a standard solution to determine the calcium concentration (or magnesium concentration) of the test solution, and the calcium concentration (or magnesium concentration) of the sample was determined by conversion from the following formula. The moisture in the sample may be measured using, for example, a KETT moisture meter (METTLER TOLEDO HB 43). About 2.0g of the sample in a water-containing state was placed in an aluminum receiving pan of a KETT hygrometer, and heated at 120℃until the weight was unchanged, whereby the moisture (weight%) in the sample was calculated from the weight changes before and after the heating.

[ number 1]

(YI value)

The YI value of the cellulose acetate particle of the present disclosure is preferably 20 or less, more preferably 19 or less, further preferably 18 or less, particularly preferably 17 or less. The lower the YI value, the less yellow tone of the cellulose acetate and the more excellent the hue are, and the lower limit of the YI value is not particularly limited and may be 10 or more.

The YI value of the cellulose acetate particle can be measured in accordance with "JIS K7373 method for determining plastics-yellowness and yellowness".

[ cellulose acetate ]

(degree of substitution of acetyl)

The cellulose acetate particles of the present disclosure contain cellulose acetate having an acetyl substitution degree of 2.2 or more and 2.6 or less. The degree of substitution of the acetyl group may be 2.3 or more, may be 2.4 or more, and may be 2.5 or less.

If the degree of substitution by acetyl groups is less than 2.2, the dimensional stability, moisture resistance, heat resistance, etc. of the resulting molded article become low. On the other hand, if the degree of substitution by acetyl groups exceeds 2.6, the resulting molded article has excellent strength, but becomes brittle, and for example, when used as a fiber material for clothing or the like, a molded article such as a frame for glasses or sunglasses, a large amount of plasticizer needs to be added to obtain flexibility such as elongation suitable for these applications, and the possibility of bleeding becomes high.

The degree of substitution of acetyl groups can be determined by the following well-known titration method: the substitution degree of cellulose acetate was determined by dissolving cellulose acetate in an appropriate solvent according to the substitution degree. The degree of substitution of acetyl groups is determined by following ASTM: the degree of acetylation obtained by the method for measuring the degree of acetylation in D-817-91 (test method for cellulose acetate and the like) is calculated by the following equation. This is the most common method for determining the substitution degree of cellulose acetate.

In the present disclosure, the degree of substitution of acetyl means the total degree of substitution of acetyl, that is, the sum of the degrees of substitution of acetyl at positions 2, 3, and 6 of the glucose ring, which is also referred to as cellulose acetate, can be replaced.

The degree of substitution of each of the acetyl groups at positions 2, 3 and 6 of the glucose ring of cellulose acetate can be determined by nuclear magnetic resonance spectroscopy (NMR) according to the method of Otsuka (Tezuka, carbonydr. Res.273, 83 (1995)) ¹³ C-NMR or ¹ H-NMR) determination.

(6% viscosity)

The cellulose acetate particles of the present disclosure may have a 6% viscosity of 50 to 120mpa·s inclusive. The 6% viscosity is preferably 55 mPas or more, more preferably 65 mPas or more, still more preferably 70 mPas or more, and particularly preferably 80 mPas or more. The 6% viscosity is preferably 110 mPas or less, more preferably 100 mPas or less, and even more preferably 90 mPas or less.

If the 6% viscosity of cellulose acetate is too low, the resulting molded article may have poor mechanical strength, in particular poor toughness. In addition, in the case of attempting to obtain a molded article, the fluidity of the molten cellulose acetate particles is too high, and the possibility of leakage from the mold becomes high. On the other hand, if the 6% viscosity is too high, the resulting molded article may have poor hue or poor mechanical strength, in particular, poor tensile properties and bending properties. In addition, in the case of attempting to obtain a molded article, fluidity of the molten cellulose acetate particles is low, and surface smoothness of the obtained molded article may be deteriorated.

Here, the 6% viscosity was determined by dissolving cellulose acetate in a 95% aqueous acetone solution so as to be 6wt/vol% and using a fluidization time using an oldham viscometer.

The 6% viscosity can be adjusted by appropriately changing the conditions such as the reaction time, the catalyst amount, the reaction temperature, and the neutralization amount in the step (2) of acetylation and the step (3) of hydrolysis in the production of cellulose acetate (sheet) described below.

[ composition sugar ratio ]

The constituent sugar ratio of the cellulose acetate of the present disclosure is preferably 97mol% or more, more preferably 97.5mol% or more, still more preferably 98.0mol% or more, and most preferably 98.5mol% or more of glucose in the sum of glucose (Glc), xylose (Xyl) and mannose (Man). The reason for this is that cellulose acetate particles having a more excellent hue and particularly high transparency can be obtained.

The ratio (mol%) of glucose in the sum of glucose, xylose and mannose can be determined by the following method.

Cellulose acetate (sample) may be hydrolyzed with sulfuric acid, neutralized with barium carbonate, filtered through a filter paper and an ion exchange filter, and then, in a High Performance Liquid Chromatography (HPLC) method, the contents of glucose, xylose and mannose may be calculated from data obtained by a high performance liquid chromatography electrospray detector (HPLC-CAD), and the ratio (mol%) of glucose in the sum of glucose, xylose and mannose may be determined.

Plasticizer (plasticizer)

The cellulose acetate particle of the present disclosure contains a plasticizer. The plasticizer is contained in an amount of 30 parts by weight or more and 44 parts by weight or less relative to 100 parts by weight of cellulose acetate. The plasticizer may be contained in an amount of 33 parts by weight or more and 35 parts by weight or more based on 100 parts by weight of cellulose acetate. Further, the content of the plasticizer may be 40 parts by weight or less.

If the plasticizer content is too small, the YI value of the cellulose acetate particle is high and the hue is poor. If the plasticizer content is too large, the YI value of the cellulose acetate particle is low, and even when an excellent hue is obtained, the mechanical strength of the obtained molded article is poor, in particular, the tensile properties and bending properties are poor.

The content of the plasticizer in the cellulose acetate particle is obtained by dissolving the cellulose acetate particle in a solvent in which the cellulose acetate particle is dissolved, subjecting the solution to ¹ H-NMR measurement was performed.

Examples of the plasticizer include the following. Aromatic carboxylic acid ester plasticizers [ phthalic acid plasticizers (dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, di-C1-12 alkyl phthalate such as di-2-ethylhexyl phthalate, C1-6 alkoxyC 1-12 alkyl phthalate such as dimethoxyethyl phthalate, C1-12 alkyl phthalate such as butylbenzyl phthalate, C1-6 alkyl phthalyl C2-4 alkylene glycol esters such as ethylphthalyl glycol ester and butylphthalyl butylene glycol ester, etc.) and trimellitic acid plasticizers (trimethyl trimellitate, triethyl trimellitate, trioctyl trimellitate, trio-C1-12 alkyl trimellitate such as trioctyl trimellitate, etc.); phosphate plasticizers [ tributyl phosphate, tricresyl phosphate, triphenyl phosphate, etc. ]; fatty acid ester plasticizers [ adipic acid esters such as dibutyl adipate, dioctyl adipate, butoxyethoxyethyl/benzyl adipate (benzoyl adipate), and dibutoxyethoxyethyl adipate; azelaic acid esters such as diethyl azelate, dibutyl azelate, and dioctyl azelate; sebacates such as dibutyl sebacate and dioctyl sebacate; butyl oleate; methyl acetyl ricinoleate, etc ]; glyceride-based plasticizers [ such as glyceryl triacetate and diglycerol tetraacetate ] which are lower fatty acid esters of polyhydric alcohols (such as glycerin, trimethylolpropane, pentaerythritol, and sorbitol); glycol ester plasticizers [ dipropylene glycol dibenzoate, etc ]; citrate plasticizers [ tributyl acetylcitrate, etc ]; an amide plasticizer [ N-butylbenzenesulfonamide, etc. ]; ester oligomer plasticizers (caprolactone oligomer, etc.); epoxidized soybean oil. These plasticizers may be used alone or in combination of two or more.

Among these plasticizers, at least one selected from the group consisting of a citrate-based plasticizer, a glyceride-based plasticizer, a phosphate-based plasticizer, and a phthalate-based plasticizer is preferably contained, and at least one selected from the group consisting of a glyceride-based plasticizer and a phthalate-based plasticizer is more preferably contained. In particular, since the cellulose acetate has excellent compatibility, it is more preferable to contain at least one selected from the group consisting of diethyl phthalate and glyceryl triacetate.

[ optional ingredients ]

The cellulose acetate particle of the present disclosure may contain any conventionally known component. Any component may be used as long as the type and amount thereof are adjusted according to the purpose and/or specification of the intended molded article. Examples of the optional component include: stabilizers such as antioxidants, ultraviolet absorbers, heat stabilizers, and light stabilizers; colorants such as dyes and pigments; an antistatic agent; a flame retardant aid; a lubricant; an anti-blocking agent; a dispersing agent; a fluidizing agent; an anti-drip agent; a chelating agent; antibacterial agents, etc. Cellulose esters other than cellulose acetate (for example, organic acid esters such as cellulose propionate and cellulose butyrate, and inorganic acid esters such as cellulose nitrate, cellulose sulfate and cellulose phosphate) may be contained as an optional component.

[ production of cellulose acetate particles ]

The cellulose acetate particle of the present disclosure is not particularly limited. For example, it is obtained by: after mixing cellulose acetate (flakes) with a plasticizer and drying to obtain cellulose acetate having a plasticizer adsorbed thereon, the cellulose acetate having a plasticizer adsorbed thereon is melt-kneaded to prepare a particulate form. Specifically, examples thereof include: a method of kneading cellulose acetate having a plasticizer adsorbed thereto by an extruder such as a single screw or twin screw extruder to form pellets, or a method of melt-kneading by a kneader such as a heated roll or a Banbury mixer to form pellets.

In the case of mixing a plasticizer with cellulose acetate (flakes), the mixing of cellulose acetate (flakes) and the plasticizer can be performed by a mixer such as a planetary mill, a henschel mixer, a vibration mill, or a ball mill. Since homogeneous mixing and dispersion can be performed in a short time, a henschel mixer is preferably used. The degree of mixing is not particularly limited, and for example, in the case of a henschel mixer, mixing for 10 minutes to 1 hour is preferable.

In addition, drying may be performed after mixing the cellulose acetate and the plasticizer. Examples of the drying method include a method of standing at 50 to 105℃for 1 to 48 hours and drying.

(production of cellulose acetate (sheet))

The cellulose acetate (sheet) can be obtained by a conventionally known production method. For example, a method for producing cellulose acetate (sheet) having the following steps: step (1), the pulp is contacted with acetic acid for pretreatment; step (2) (acetylation step) of, after the pretreatment, allowing cellulose contained in the pulp to react with acetic anhydride to perform acetylation; a step (3) (aging step) of hydrolyzing the cellulose acetate obtained by the acetylation; and (4) precipitating the cellulose acetate having the degree of substitution of the peracetyl group adjusted by the hydrolysis.

Pulp may be used as a cellulose source that becomes a raw material for cellulose acetate of the present disclosure. Examples of the pulp include wood pulp and cotton linter pulp (linter pulp). In particular wood pulp can be used.

In the step (1) of pretreating the pulp by bringing it into contact with acetic acid, acetic acid or acetic acid (sulfuric acid) containing 1 to 10% by weight of sulfuric acid may be used.

In the step (2) of acetylating cellulose contained in the pulp by reacting with acetic anhydride, the acetylating may be specifically started, for example, by the following means: adding cellulose contained in pulp activated by pretreatment to a mixture of acetic acid, acetic anhydride and sulfuric acid; or adding a mixture of acetic acid and acetic anhydride and sulfuric acid to cellulose contained in pulp activated by pretreatment.

The cellulose acetate is in a state in which almost all hydroxyl groups are substituted with acetyl groups by the above-mentioned acetylation, and hydrolysis may be performed to adjust the degree of substitution to a desired degree. In the case where sulfuric acid is used as the catalyst for the acetylation reaction, since the sulfuric acid is bonded to cellulose as a sulfate, the step (3) of hydrolyzing is also aimed at removing the sulfate by hydrolysis in order to improve the thermal stability after the completion of the acetylation reaction.

In the step (3) of performing hydrolysis, the degree of substitution of acetyl groups can be adjusted by stopping the acetylation reaction by adding a neutralizing agent composed of water (including water vapor); dilute acetic acid; or carbonates, acetates, hydroxides or oxides of calcium, magnesium, iron, aluminum or zinc, etc.

In the step (4) of precipitating the cellulose acetate whose acetyl substitution degree is adjusted by the hydrolysis, a mixture containing cellulose acetate may be mixed with a precipitating agent such as water or dilute acetic acid, and the formed cellulose acetate (precipitate) may be separated to obtain a precipitate. In addition, dilute acetic acid is preferable as a precipitant.

After the step (4) of precipitating the cellulose acetate, the free metal component, sulfuric acid component and the like may be removed by washing with water. In addition to the water washing, the following substances may be further added as stabilizers as needed: alkali metal compounds and/or alkaline earth metal compounds, in particular calcium compounds such as calcium hydroxide. In addition, a stabilizer may be used in washing with water.

The cellulose acetate may be dried immediately after the step (4) of precipitating the cellulose acetate or after any step such as washing with water. The drying method is not particularly limited, and a known method may be used, and for example, drying may be performed under conditions such as air blowing or reduced pressure. As a drying method, for example, hot air drying is mentioned.

[ molded article ]

The cellulose acetate particles of the present disclosure may also be redissolved, for example, using a single screw or twin screw extruder with a T die attached, for shaping processing. The cellulose acetate particle of the present disclosure may be molded by a conventionally known molding method. Specific molding methods include: injection molding, extrusion molding, vacuum molding, profile molding, foam molding, injection molding (injection press), press molding, blow molding (blow molding), gas injection molding, and the like.

The shape of the molded article obtained by the molding process of the cellulose acetate particle of the present disclosure is not particularly limited, but may be, for example, particles, films, sheets, fibers, or the like. The shape of the molded article may be adjusted according to various applications such as OA (Office Automation: office automation)/home appliances, electric/electronic appliances, communication equipment, sanitary appliances, transportation vehicles such as automobiles, housing-related fields such as furniture and building materials, and sundry goods.

The aspects disclosed herein can be combined with any of the other features disclosed herein.

Examples

Hereinafter, the present disclosure will be specifically described by way of examples, but the technical scope thereof is not limited by these examples.

The physical properties described in examples below were evaluated by the following methods.

< degree of acetylation/degree of substitution of acetyl >

The degree of acetylation of cellulose acetate was determined by a method for measuring the degree of acetylation in ASTM-D-817-91 (test method for cellulose acetate and the like). 1.9g of dried cellulose acetate was weighed precisely, dissolved in 150mL of a mixed solvent of acetone and dimethyl sulfoxide (capacity ratio: 4:1), and then 30mL of a 1N-sodium hydroxide aqueous solution was added thereto to saponify the mixture at 25℃for 2 hours. Phenolphthalein was added as an indicator and excess sodium hydroxide was titrated with 1N-sulfuric acid (concentration factor: F). Further, a blank test was performed by the same method as described above, and the degree of acetylation was calculated according to the following formula.

Degree of acetylation (%) = [6.5× (B-ase:Sub>A) ×f ]/W

(wherein A represents the titration amount (ml) of 1N-sulfuric acid in the sample, B represents the titration amount (ml) of 1N-sulfuric acid in the blank test, F represents the concentration factor of 1N-sulfuric acid, and W represents the weight of the sample).

The degree of substitution of acetyl groups is obtained by converting the degree of acetylation into the following formula.

DS＝162.14×AV×0.01/(60.052-42.037×AV×0.01)

DS: degree of substitution of acetyl group.

AV: degree of acetylation (%).

<6% viscosity >

The 6% viscosity of cellulose acetate was determined by the following method. To the flask, 3.00g of the dried sample and 61.67g of methylene chloride were added, and the mixture was stirred for about 1 hour with a cover. Then, the mixture was completely dissolved by shaking with a tumbling shaker for about 1.5 hours. The resulting 6wt/vol% solution was transferred to the reticle of a specific Orthometer and temperature was adjusted at 25.+ -. 1 ℃ for about 30 minutes. The flow down time between the time lines was measured, and the 6% viscosity was calculated according to the following formula (1).

6% viscosity (mPa.s) =flow down time(s). Times.viscometer coefficient (1)

The coefficient of the viscometer was determined by measuring the flow down time by the same procedure as described above using a standard liquid for viscometer correction [ trade name "JS-200" (according to JIS Z8809) manufactured by Showa Petroleum Co., ltd., from the following formula (2).

Viscometer coefficient= { standard solution absolute viscosity (mPa.s). Times.solution Density (0.827 g/cm) ³ ) Density of the }/{ Standard solution (g/cm) ³ ) Flow-down seconds of X standard solution(s) } (2)

< YI value (yellow index value) >)

The YI value of cellulose acetate is the YI value of the transmitted light of the cellulose acetate solution measured. The apparatus was manufactured by the electric color industry of Japan under the trade name "Spectro Color Meter SQ" and the measurement conditions were selected so as to have a measurement diameter of 30mm, a C light source, a 2 DEG visual field, and EXCLUDE (no specular reflection). To 12g of dried cellulose acetate, 8.8g of methanol and 79.2g of methylene chloride were added to dissolve the mixture, and the defoamed solution was put into a 45mm (L). Times.45 mm (W). Times.10 mm (D) glass test cell to determine YI value. The lower YI value means that the less yellow tone of cellulose acetate and the more excellent hue are.

< constituent sugar ratio >

Cellulose acetate was hydrolyzed with sulfuric acid, neutralized with barium carbonate, filtered through a filter paper and an ion exchange filter, and the molar contents of glucose, xylose and mannose were calculated using data obtained by HPLC-CAD (Agilent 1200 series system) in a High Performance Liquid Chromatography (HPLC) method, and the ratio of the molar contents of glucose (Glc), xylose (Xyl) and mannose (Man) was calculated.

The HPL-CADC measurement conditions are as follows.

Chromatographic column: asahipak NH2P-50 e (4.6 mm i.d.×250 mm).

Protective column: asahipak NH2P-50g 4a (4.6 mm i.d.×10 mm).

Chromatographic column temperature: 20 ℃.

Mobile phase: water/acetonitrile=25/75 (v/v).

Mobile phase flow rate: 1.0mL/min.

A detector: coronaplus CAD detector (ESA Biosciences).

Nitrogen pressure: 35psi.

Atomizer: 30 ℃.

< tensile Strength at yield point, tensile Strength at breaking point, and elongation >

The cellulose acetate pellets were extruded by a twin-screw extruder, formed into a sheet having a thickness of 6.4mm, and punched to prepare a test piece in the form of a long strip (dumbbell No. 1). The tensile strength at yield point was determined under conditions of a tensile speed of 5mm/min according to ASTM-D638 using the dumbbell No. 1. The tensile strength and elongation at break were determined in accordance with ASTM-D638 using the dumbbell No. 1.

< flexural Strength and flexural modulus >

The flexural strength and flexural modulus of the cellulose acetate pellets were determined according to ASTM-D790 using an elongated sheet (127 mm. Times.12.7 mm. Times.6.4 mm) obtained by extruding cellulose acetate pellets using a twin-screw extruder, molding the extruded sheet into a sheet having a thickness of 6.4mm, and punching the sheet.

< impact Strength of cantilever beam >

The cantilever impact strength of the cellulose acetate pellets was determined according to ASTM-D256 using a long sheet (63.5 mm. Times.12.7 mm. Times.6.4 mm) obtained by extruding cellulose acetate pellets using a twin screw extruder, molding the extruded cellulose acetate pellets into a sheet having a thickness of 6.4mm, and punching the sheet.

< Rockwell hardness >

The Rockwell hardness of the cellulose acetate particle was determined according to ASTM-D785.

< heat deformation temperature (high load) >)

The heat distortion temperature of the cellulose acetate particle was determined by using a long sheet according to ASTM-D648.

< Melt Flow Rate (MFR) >)

The MFR of the cellulose acetate particle was determined in accordance with JIS-K7210 under conditions of a temperature of 200℃and a load of 2.16 kg.

< calcium concentration/magnesium concentration >

3.0g of an undried sample was measured in a crucible, carbonized by an electric heater, and then ashed in an electric furnace at 750℃or higher and 850℃for about 2 hours. After cooling for about 30 minutes, 25mL of a 0.07 wt% hydrochloric acid solution was added, and the mixture was heated and dissolved at 220 to 230 ℃. After cooling, the dissolved solution was fixed to 200mL with distilled water, and the absorbance was measured with an atomic absorption spectrometer together with a standard solution to determine the calcium concentration (or magnesium concentration) of the test solution, and the calcium concentration (or magnesium concentration) of the sample was determined by conversion from the following formula. The moisture in the sample is measured using, for example, a KETT moisture meter (METTLER TOLEDO HB) 43. About 2.0g of the sample in a water-containing state was placed in an aluminum receiving pan of a KETT hygrometer, and heated at 120℃until the weight was unchanged, whereby the moisture (weight%) in the sample was calculated from the weight changes before and after the heating.

< Total sulfuric acid >

The total sulfuric acid of the cellulose acetate particle was obtained as follows. An electrolyte solution in which sodium azide, acetic acid and potassium iodide were added to distilled water was prepared in a titration cell. About 0.01g of the dried cellulose acetate particles (test pieces) were placed in a quartz boat, burned in a tubular furnace in an argon/oxygen stream at 800-900 c, and the resulting sulfur dioxide was introduced into the electrolyte of the titration cell. A tri-iodide ion is generated in the titration cell by electrolysis, sulfur dioxide is titrated with the tri-iodide ion, and the amount of sulfuric acid is calculated from the amount of electricity required for the titration. The dibutyldisulfide/toluene standard solution was combusted in the same manner, and the sulfuric acid amount of the sample was corrected based on the recovery rate, and the result was used as total sulfuric acid. Total sulfuric acid is expressed in ppm units as the amount of sulfuric acid in 1g of cellulose acetate particle in absolute dry state.

< YI value (yellow index value) >)

YI value of the cellulose acetate particle was measured according to "JIS K7373 method for determining plastics-yellowness and yellowness". The apparatus used a spectrocolorimeter SD7000 manufactured by Nippon electric color industries Co., ltd.) under the measurement conditions D65 as a light source and a 10℃viewing angle and reflectance (SCE) as a measurement method. To the direction ofParticles were added to the 15H round tank and vibrated up and down about 20 times, and the YI value was measured by scraping with a rod or a spatula. The measurement value was an average value obtained by measuring 5 times.

Example 1]

The conifer pre-hydrolyzed sulfite pulp having an alpha cellulose content of 97.7wt% was broken into cotton-like pulp using a disc refiner to obtain broken pulp. 26 parts by weight of acetic acid was sprayed onto 100 parts by weight of crushed pulp (water content: 7.0%) and stirred sufficiently, and then left to stand for 1.6 hours as a pretreatment for activation (activation step).

The activated pulp was added to a mixture of 310 parts by weight of acetic acid, 250 parts by weight of acetic anhydride, and 13.3 parts by weight of sulfuric acid. The mixture was pre-cooled to-12 ℃. The maximum temperature of 46℃was adjusted from-16℃over 40 minutes, and 110 minutes of acetylation was performed from the point in time when the pulp was added to the mixture (acetylation step). The neutralizing agent (24% magnesium acetate aqueous solution) was added over 3 minutes so that the amount of sulfuric acid (the amount of aged sulfuric acid) was adjusted to 2.5 parts by weight. Then, after adding water so that the concentration of the water in the reaction bath (aged water) became 60mol%, the reaction bath was heated to 85℃over 55 minutes. The aging water concentration was obtained by multiplying the ratio of the reaction bath water to acetic acid in terms of mole ratio by 100 in terms of mole%. Then, aging was performed at 85℃for 80 minutes, and the aging was stopped by neutralizing sulfuric acid with magnesium acetate, thereby obtaining a reaction mixture containing cellulose acetate (aging step).

Dilute acetic acid (10 wt%) was mixed into the resultant reaction mixture containing cellulose acetate using a twin screw kneader, and cellulose acetate was precipitated by mixing into a precipitation system. At this time, dilute acetic acid was mixed into the reaction mixture containing cellulose acetate in 5 portions.

The precipitated cellulose acetate was washed with water, immersed in a dilute calcium hydroxide aqueous solution (20 ppm), filtered off, dried, and pulverized with a pulverizer to obtain a cellulose acetate sheet.

Using a henschel mixer, 100 parts by weight of cellulose acetate sheet, 35.5 parts by weight of diethyl phthalate (DEP of large octa chemical industry (ltd)) as a plasticizer, 0.3 parts by weight of tris (2, 4-di-t-butylphenyl) phosphite as an antioxidant (peroxide decomposer), 0.5 parts by weight of epoxidized soybean oil as a plasticizer and a heat stabilizer, and 0.02 parts by weight of citric acid as a metal chelator for preventing radical reaction were stirred and mixed, and then fed to a twin screw extruder (melting temperature (barrel temperature: actual temperature: 194 ℃ C., die set temperature: 205 ℃ C.) to extrude and granulate, thereby obtaining cellulose acetate pellets.

< examples 2 to 5>

For examples 2 to 5, the concentration of the dilute calcium hydroxide aqueous solution was reduced (example 2); shortening the time of the acetylation process and reducing the amount of water added in the ripening process (examples 3 and 5); a cellulose acetate sheet was obtained in the same manner as in example 1, except that the raw material was changed to cotton linter pulp (example 4). Cellulose acetate pellets were obtained in the same manner as in example 1 except that the temperature at the time of producing cellulose acetate pellets using the cellulose sheet was adjusted as shown in table 1.

Example 6 ]

Cellulose acetate pellets were obtained in the same manner as in example 1, except that glyceryl triacetate was used as a plasticizer.

Comparative examples 1 and 2

For comparative examples 1 and 2, the concentration of the dilute calcium hydroxide aqueous solution was set to 25ppm (comparative example 1); cellulose acetate flakes were obtained in the same manner as in example 1 except that the concentration of the dilute aqueous calcium hydroxide solution was changed to 10ppm (comparative example 2). Cellulose acetate pellets were obtained in the same manner as in example 1 except that the cellulose sheet was used.

Comparative examples 3 to 4 ]

Cellulose acetate pellets were obtained in the same manner as in comparative example 1 except that the amount of plasticizer to be mixed was as shown in table 1.

Comparative example 5 ]

In the washing of the precipitated cellulose acetate with water, the temperature and amount of water were changed to obtain a cellulose acetate flake having a high total sulfuric acid content. Further, using the cellulose sheet, cellulose acetate pellets were obtained in the same manner as in example 1.

Comparative examples 6 to 7 ]

In comparative examples 6 to 7, the time of the acetylation step was prolonged, and the amount of water added in the aging step was increased (comparative example 6); cellulose acetate flakes having a viscosity of 6% were obtained in the same manner as in example 1, except that the time of the acetylation step was shortened and the amount of water added in the aging step (comparative example 7) was reduced. Cellulose acetate pellets were obtained in the same manner as in example 1 except that the temperature at the time of producing cellulose acetate pellets using the cellulose sheet was set as shown in table 1.

The results of the measurement of the physical properties of each of the cellulose acetate flakes and cellulose acetate particles in the above examples and comparative examples are shown in table 1.

TABLE 1

In comparative examples 1 and 2, the calcium concentration of comparative example 1 was high and the calcium concentration of comparative example 2 was low, compared with the examples, so that the YI value of the cellulose acetate particle was high, that is, yellow tone was strong and color difference was poor.

In comparative example 6, the MFR was low and the YI value of the cellulose acetate particle was high as compared with the examples. In comparative example 3, since the MFR was low and the plasticizer content was also low, the YI value of the cellulose acetate particle was higher and the hue was poor.

In comparative example 4, the YI value was low even though the MFR was high because the plasticizer content was large, but the tensile strength at break, the flexural strength, the flexural modulus, the Rockwell hardness and the heat distortion temperature (high load) were low, and the tensile properties and flexural properties were poor. That is, it is known that the deformation is easy.

In comparative example 5, the total sulfuric acid was high and the YI value of the cellulose acetate particle was high as compared with the example.

In comparative example 7, the MFR was higher than that of the example. Therefore, cellulose acetate particles have low YI value and excellent hue, but have low Izod impact strength and poor toughness. That is, it is known that the impact is not resistant.

On the other hand, since the cellulose acetate particle of example has a low YI value and an excellent hue and other physical properties are also excellent, it is found that a molded product of cellulose acetate having excellent strength and high transparency is obtained.

Claims

1. A cellulose acetate particle comprising cellulose acetate and a plasticizer,

a melt flow rate exceeding 1.0g/10min and less than 2.8g/10min, a total sulfuric acid of 20ppm or more and 170ppm or less, and a calcium concentration of 22ppm or more and 37ppm or less,

the cellulose acetate has an acetyl substitution degree of 2.2 or more and 2.6 or less,

the plasticizer is contained in an amount of 30 parts by weight or more and 44 parts by weight or less relative to 100 parts by weight of the cellulose acetate.

2. The cellulose acetate particle according to claim 1, wherein,

the plasticizer includes at least one selected from the group consisting of glyceride-based plasticizers and phthalic acid-based plasticizers.

3. The cellulose acetate particle according to claim 1 or 2, wherein,

YI value is 20 or less.

4. The cellulose acetate particle according to claim 1 or 2, wherein,

the melt flow rate is 1.2g/10min or more and 2.3g/10min or less.

5. The cellulose acetate particle according to claim 1, wherein,

the cellulose acetate has a 6% viscosity of 50 mPas to 120 mPas.

6. The cellulose acetate particle according to claim 1, wherein,

the magnesium concentration of the cellulose acetate particle is 1ppm to 50 ppm.

7. The cellulose acetate particle according to claim 1, wherein,

the total concentration of calcium and magnesium in the cellulose acetate particles is 0.5 [ mu ] mol/g or more and 3 [ mu ] mol/g or less.