Vinyl polymer microparticles, and masterbatch and resin film containing the same

Abstract

Provided are vinyl polymer microparticle which can reduce an average volume of the microparticles dropping off from a film surface while reducing the friction of the film. The vinyl polymer microparticles satisfy the following (1) to (3): (1) a coefficient of variation of particle sizes is 30% or more on a volume basis; (2) a proportion of vinyl polymer microparticles having a particle size of 1.7 times or more and 2.5 times or less a volume average particle size is 0.040% or less on a number basis; and (3) a volume average particle size is 3.7 μm or more.

Claims

1. Vinyl polymer microparticles that satisfy the following (1) to (3): (1) a coefficient of variation of particle sizes is 30% or more on a volume basis; (2) a proportion of vinyl polymer microparticles having a particle size of 1.7 times or more and 2.5 times or less a volume average particle size is 0.040% or less on a number basis; and (3) a volume average particle size is 3.7 μm or more, wherein the vinyl polymer microparticles comprise a copolymer of a (meth)acrylic monofunctional monomer and a (meth)acrylic difunctional crosslinkable monomer.

2. The vinyl polymer microparticles according to claim 1, wherein the (meth)acrylic monofunctional monomer is a C.sub.1-4 alkyl(meth)acrylate, and the (meth)acrylic difunctional crosslinkable monomer is an alkanediol di(meth)acrylate.

3. The vinyl polymer microparticles according to claim 1, wherein a residual amount of a (meth)acrylic monomer is 700 ppm or less.

4. A masterbatch comprising the vinyl polymer microparticles according to claim 1 and a resin.

5. The masterbatch according to claim 4, wherein the resin is a polyolefin resin.

6. A resin film comprising the vinyl polymer microparticles according to claim 1 and a resin.

7. The resin film according to claim 6, wherein a content of the vinyl polymer microparticles is 0.01% by mass or more and 10% by mass or less.

8. The resin film according to claim 6, wherein the resin film has a thickness of 0.1 μm or more and 1 mm or less.

Description

EXAMPLES

(1) Hereinafter, the present invention is described in more detail by way of examples. The present invention is, however, not limited to the following examples in any way, and it is possible to work the present invention according to the examples with an additional appropriate change within the range of the above descriptions and the following descriptions. Such a changed embodiment is also included in the technical scope of the present invention.

(2) (1) Particle Size and Coefficient of Variation

(3) About 0.1 g of vinyl polymer microparticles was well dispersed in 0.5 g of a surfactant (“NEOPELEX (registered trademark) G-15”, sodium dodecylbenzene sulfonate, manufactured by Kao Corp.), and the dispersion was irradiated with ultrasound for 5 minutes. Then, 15 g of deionized water was added to the obtained dispersed viscous liquid. Thereafter, ultrasonic wave was applied to the mixture to prepare a vinyl polymer microparticle dispersion in a particle dispersed state. Using a precision grain size distribution measuring device (“Coulter Multisizer III” manufactured by Beckman Coulter, Inc., at an aperture of 50 μm), particle sizes of 100,000 microparticles were measured, and an average particle size on a volume basis and a coefficient of variation of the particle size were determined.

(4) Coefficient of variation of particle size (%)=(σ/d50)×100

(5) Here, the “σ” represents a standard deviation of the particle size on a volume basis, and the “d50” represents an average particle size (volume average particle size) on a volume basis.

(6) (2) Proportion of Vinyl Polymer Microparticles Having a Particle Size of Times or More and 2.5 Times or Less a Volume Average Particle Size

(7) Using a flow type particle image analyzer (“FPIA-3000 (registered trademark)”: Sysmex Corporation), particle size distribution data on a number basis was obtained for 1 million vinyl polymer microparticles as a measurement target. Based on the particle size distribution data, all the shapes were checked in the image, and the shapes of all the microparticles having a particle size of 1.7 times or more and 2.5 times or less a volume average particle size obtained in the above (1) were checked, and the number of vinyl polymer microparticles having a circularity of 0.95 or more was counted. In addition, since particles having a circularity of less than 0.95 are agglomerated particles, they were not counted as coarse particles even with a predetermined particle size. This measurement was repeated four times, and the average value was defined as the number of vinyl polymer microparticles having a particle size of 1.7 times or more and 2.5 times or less a volume average particle size on a number basis. The percentage determined by dividing the above average value by 1,000,000 was taken as a proportion on a number basis of the vinyl polymer microparticles having a particle size of 1.7 times or more and 2.5 times or less a volume average particle size. In the above measurement, HPF (high magnification imaging) mode/quantitative counting method (total count number 250,000, repeated measurement number 1) was set as a measurement condition of flow type particle image analyzer (“FPIA-3000 (registered trademark)”) in such a manner that 17.5 parts of a 1.4% by mass aqueous surfactant solution (NEOPEREX (registered trademark) G-15 (sodium dodecylbenzene sulfonate) manufactured by Kao Corporation) were added to the dispersion (0.05 parts in terms of particles) or 0.05 parts of the particle powder, and the mixture was dispersed by ultrasonic wave for 10 minutes.

(8) (3) Measurement of Coefficient of Friction (COF)

(9) A smoother surface side of a laminated resin film (biaxially stretched polypropylene film (BOPP)) after biaxial stretching was used as a measurement surface, and an autograph AG-K manufactured by Shimadzu Corporation was used as a friction coefficient measuring device. As jigs for measuring the coefficient of friction, a load cell having a capacity of 50 N, a specialized base (200 mm in width×355 min in length) for measuring friction coefficient, and a moving weight (size: 63.5 mm in width×63.5 mm in length×6.4 mm in thickness, mass of 200 g) were used.

(10) Two sheets (one set) of laminated resin films after biaxial stretching were prepared, and their peripheral portions were cut. Then, a sample film of 12 cm×18 cm and a sample film of 12 cm×12 cm were cut out respectively. Then, the cut-out film of 12 cm×18 cm was fixed to the measurement base with the roll surface facing upward and serving as the frictional resistance measurement surface, and four corners of the sample were secured with a cellophane tape. The moving weight was wrapped with the cut-out film of 12 cm×12 cm so that the roll face side comes outward and fixed to the weight with a cellophane tape.

(11) The moving weight wrapped with the sample (film) was placed on the sample (film) on the measurement base, and the moving weight was repeatedly slid in the same direction using a crosshead (speed: 150 mm/min; travel distance per sliding: 100 mm). The travel resistance generated by the friction during this sliding was measured, and a coefficient of static friction μ.sub.s and a coefficient of kinetic friction μ.sub.k were determined as follows.

(12) Coefficient of static friction μ.sub.s=Maximum tensile test force at the start of moving weight/(Mass of moving weight×gravitational acceleration)

(13) Coefficient of kinetic friction μ.sub.k=Average tensile test force during travel of moving weight/(Mass of moving weight×gravitational acceleration)

(14) The travel distances 100 mm and the distance to determine the coefficient of kinetic friction was in the range of 30 mm to 90 mm from the travel start point. The weight was allowed to continuously travel four times to measure a coefficient of static friction μ.sub.s and a coefficient of kinetic friction μ.sub.k each time. And an average value of four times was determined as the coefficient of static friction μ.sub.s and the coefficient of kinetic friction μ.sub.k.

(15) (4) Number of Drop-off particles

(16) The surface of the obtained film sample after friction test was observed (secondary electronic image) at an acceleration voltage of 5 kV using an SEM (scanning electron microscope) VK-8500 (manufactured by Keyence Corporation).

(17) For each film sample, 19 sheets of an area of 270 μm×200 μm were photographed at a 500×field of view, and a total area of 1 mm.sup.2 was photographed. The number of particles (the number of protrusions derived from vinyl polymer microparticles) and the number of drop-off particles (traces of drop-off particles) contained in each photographed image were counted, and a drop-off rate was determined based on the following equation.
Drop-off rate (%)=Number of drop-off particles/Number of particles+Number of drop-off particles)
(5) Measurement of Volume of Drop-Off Particles

(18) Except for setting the number of travels of a weight to 20 times, the weight wrapped with a film was run on a film fixed to a measurement base in the same manner as in the measurement of the coefficient of kinetic friction μ.sub.k. After that, drop-off particles adhering to the friction surface of a sample (film) fixed to the moving weight and the friction surface of the sample (film) set on the measurement base were washed away with methanol, and methanol was concentrated to dryness to collect the drop-off particles in methanol. The collected drop-off particles were observed by SEM (scanning electron microscope, VK-8500 (manufactured by Keyence Corporation)), and a particle size of the observed particles was measured using a caliper. In order to ensure the reliability of the measurement values, 300 or more drop-off particles were measured. A particle size of one drop-off particle was measured, and a particle volume of the drop-off particle was determined using the following equation. Then, after determining a particle volume of each drop-off particle for the number of “observation number” described in Table 1, all the particle volumes for the number of “observation number” were totaled to obtain a total volume of drop-off particles. Furthermore, a particle volume per drop-off particle was calculated by dividing the total volume of the drop-off particles by the number of the drop-off particles (the “observation number” described above).

(19) Particle volume=(4/3)×π×(particle radius).sup.3

(20) (6) Residual Amount of (Meth)acrylic Monomer in Vinyl Polymer Microparticles (Residual Amount of Methyl Methacrylate (MMA) in Vinyl Polymer Microparticle)

(21) About 0.2 g of vinyl polymer microparticles and 0.015 g of butylbenzene (internal standard) were mixed with 10 g of acetonitrile, and the remaining methyl methacrylate (MMA) was extracted by stirring for 2 hours or more. Thereafter, the extract was filtered with a filter having a pore diameter of 0.45 μm or less, and the amount of methyl methacrylate (MMA) in the filtrate was determined by gas chromatography using a calibration curve method, so that the amount of methyl methacrylate (MMA) in the vinyl polymer microparticles was determined. The gas chromatography conditions were as follows.

(22) Device: “GC-2014” manufactured by Shimadzu Corporation

(23) Column: DB-5MS (manufactured by J&W Scientific Inc.) 30 m in length, column diameter 0.53 mm, liquid phase film thickness 1.50 μm

(24) Vaporization chamber temperature: 280° C.

(25) Detector temperature: 320° C.

(26) Injection volume: 0.5 μL.

(27) Carrier gas (helium): Total flow 10 mL/min, purge flow 3.0 mL/min

(28) Column temperature program: kept at 50° C. (5 minutes from the start).fwdarw.temperature rise at 2° C./min (up to 60° C.).fwdarw.temperature rise at 10° C./min (up to 150° C.).fwdarw.kept at 150° C. (for 3 minutes).fwdarw.temperature rise at 2° C./min (up to 164° C.).fwdarw.temperature rise at 20° C./min (up to 300° C.).fwdarw.kept at 300° C. (for 25 minutes)

(29) Retention time of MMA: about 3.5 minutes

(30) (7) Hydrophobicity of Microparticles

(31) A glass container having a cross-sectional area of 5 cm.sup.2 or more and 10 cm.sup.2 or less was prepared, then filled with 20 mL of deionized water having a liquid temperature of 20° C. that was adjusted using a constant temperature bath. Vinyl polymer microparticles are gently floated on the water surface, and the time taken for the first particle to start sedimentation is determined to be a sedimentation start time. The hydrophobicity of microparticles was evaluated according to the following criteria

(32) A: The sedimentation time is 16 seconds or more.

(33) B: The sedimentation time is less than 16 seconds.

Example 1

(34) <Preparation of Vinyl Polymer Microparticles>

(35) A flask equipped with a stirrer, an inert gas inlet tube, a reflux condenser, and a thermometer was charged with 523 parts by mass of deionized water in which 1.8 parts by mass (0.5% by mass with respect to the monomer described below) of a polyoxyethylene distyryl phenyl ether sulfate ammonium salt (trade name “HITENOL (registered trademark) NF-08”, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) had been dissolved. The flask was then charged with the following components prepared in advance: 288 parts by mass of methyl methacrylate (MMA) and 72 parts by mass of ethylene glycol dimethacrylate (EGDMA) as a monomer, 6.84 parts by mass (1.9 parts by mass with respect to the mass of the monomer) of lauryl peroxide (product name: “PEROYL L”, manufactured by NOF Corporation) (alias name: dilauroyl peroxide) (abbreviated as LPO) as a polymerization initiator (B), 3.6 parts by mass (1.0% by mass with respect to the mass of the monomer) of t-hexylperoxy-2-ethylhexanoate (trade name “PERHEXYL O”, manufactured by NOF Corporation) (abbreviated as PHO) as a polymerization initiator (A), and 1.8 parts by mass (0.5% by mass with respect to the monomer) of a hindered phenol antioxidant (manufactured by BASF Japan, trade name “IRGANOX (registered trademark) 1010”, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) as an antioxidant. The charged mixture was stirred at 4700 rpm for 30 minutes using a T. K. Homo Mixer model 2.5 (manufactured by Primix Corporation), to give a homogeneous suspension.

(36) Into the monomer suspension, 900 parts by mass of deionized water was added. The mixture was transferred to a polymerization vessel filled with nitrogen gas, and heated until the reaction solution reached 65° C. while blowing nitrogen gas. The reaction container was kept at 65° C., and the reaction start time was determined at a time when the liquid temperature reached a peak temperature (about 80° C.) by self-heating. Stirring was continued for 1.5 hours while keeping the reaction solution at 75° C. (when the amount of the polymerization initiator is large, the jacket temperature is appropriately adjusted so that the peak temperature does not exceed 85° C.). Thereafter, the polymerization solution was further heated to 85° C. and stirred for 4 hours to complete the polymerization reaction. Then, the reaction solution (suspension) was cooled to 50° C. or less and filtered to collect a polymerization product. The polymerization product was dried at 85° C. for 14 hours using a hot air drier (manufactured by Yamato Scientific Co., Ltd.) to obtain vinyl polymer microparticles.

(37) Since the dried vinyl polymer microparticles thus obtained were agglomerated due to drying, the agglomerate was pulverized under a pulverization pressure of 0.3 MPa at a normal temperature using Super Jet Mill SJ-500 (manufactured by Nissin Engineering Inc.), thereby to obtain vinyl polymer microparticles.

(38) <Preparation of Film>

(39) Ten parts of the vinyl polymer microparticles thus produced, 90 parts of pellets of polypropylene (NOVATEC (registered trademark) FY4 manufactured by Japan Polypropylene Corporation), and 0.5 parts of IRGANOX (registered trademark) 1010 and 0.5 parts of IRGAFOS (registered trademark) 168 manufactured by BASF Japan as antioxidants were mixed using a same-direction rotating biaxial extruder (HK-25D) manufactured by Parker Corporation. The mixture was melted and kneaded at 212° C. and then cooled with water to give a strand. The strand was appropriately cut to prepare a polypropylene masterbatch including 10% of vinyl polymer microparticles.

(40) Using the polypropylene masterbatch thus obtained and polypropylene pellets, a three-layered cast film composed of two kinds of materials was prepared. A structure which laminates a surface layer on both surfaces of a base film was adopted. A T-die extruder (manufactured by Souken Co., Ltd.) was used for the film preparation. In the surface layer of the two layers, 1 part by mass of a masterbatch containing 10% of vinyl polymer microparticles, and 9 parts by mass of polypropylene pellets were used, and 180 parts of polypropylene pellets alone were used as a base film. In the cast film, the average thickness of the two surface layers was 16 μm, the average thickness of the base film was 288 μm, and the total average thickness of the two surface layers and the base film was 320 μm.

(41) The cast film thus obtained was cut into a piece having a length of 9 cm and a width of 9 cm. The cut film piece was subjected to simultaneous biaxial stretching under heating conditions of 165° C. with a stretch ratio set to 3 times in longitudinal and lateral directions using a simultaneous biaxial stretching machine (manufactured by Toyo Seiki Co., Ltd.). The obtained film had a size of 22 cm×22 cm. The center portion of the stretched film had a thickness of about 20 μm, while the film end portion had a thickness of about 100 μm, and a central 12 cm square of the stretched film was cut out.

(42) The average thickness of the entire film was calculated by further cutting out a central 10 cm square of the cut film, measuring the thickness 3 times or more with a micrometer (MDC-25M manufactured by Mitutoyo Corporation), and calculating the average value. In addition, each average thickness of the surface layer and the base film was calculated by embedding the film in an epoxy resin, polishing the resin so that the cross section of the film is exposed to the surface, observing the cross section by an SEM (scanning electron microscope), measuring the thickness of the film at equally three-divided positions, and averaging the measured values. The total thickness of the film was 20 μm, the average thickness of each of the two surface layers was 1 μm, and the average thickness of the base film was 18 μm.

(43) In addition, the film formed from the T-die extrusion molding machine is obtained by winding up when producing a cast film. A side to be in contact with a winding roll is called a roll surface, and the other side is called an air surface. In general, crystal growth of the polypropylene can be suppressed on the roll surface side because of high cooling speed, so that the completed roll surface side of the cast film is smooth. On the other hand, crystal growth of the polypropylene easily occurs on the air surface side, so that micro unevenness is present compared to the roll surface side.

(44) Various physical properties of the vinyl polymer microparticles and the film are shown in Table 1.

Comparative Example 1

(45) Vinyl polymer microparticles and a film were produced in the same manner as in Example 1 except that the stirring was performed at 5500 rpm for 10 minutes. Table 1 shows various physical properties of the vinyl polymer microparticles and the film.

Example 2

(46) Vinyl polymer microparticles and a film were produced in the same manner as in Example 1 except that the stirring was performed at 4500 rpm for 30 minutes, Table 1 shows various physical properties of the vinyl polymer microparticles and the film.

Comparative Example 2

(47) Vinyl polymer microparticles and a film were produced in the same manner as in Example 1 except that the stirring was performed at 5000 rpm for 10 minutes. Table 1 shows various physical properties of the vinyl polymer microparticles and the film.

Comparative Example 3

(48) Vinyl polymer microparticles and a film were produced in the same manner as in Example 1 except that the amount of polyoxyethylene distyryl phenyl ether sulfate ammonium salt (trade name “HITENOL (registered trademark) NF-08”, manufactured by Dai-ichi Kogyo Seiyaku. Co., Ltd.) was changed to 3.6 parts by mass (1.0% by mass with respect to the mass of the monomer), the amount of the polymerization initiator (A) was changed to 0 part by mass (without charging the polymerization initiator (A)), the amount of LPO as the polymerization initiator (B) was changed to 3.6 parts by mass (1.0% by mass with respect to the mass of the monomer), and the stirring was performed at 5500 rpm for 40 minutes. Table 1 shows various physical properties of the vinyl polymer microparticles and the film.

Comparative Example 4

(49) Vinyl polymer microparticles and a film were produced in the same manner as in Comparative Example 3 except that the stirring was performed at 5700 rpm. Table 1 shows various physical properties of the vinyl polymer microparticles and the film.

Comparative Example 5

(50) Vinyl polymer microparticles were produced in the same manner as in Example 1 except that the stirring was carried out at 5650 rpm for 10 minutes, and after stirring, classification was performed using a Micro Separator (registered trademark) MS-1H (manufactured by Hosokawa Micron Corporation) under the conditions of a classification rotation speed 3500 rpm, an air volume 15 m.sup.3/min, and a coarse powder cut rate 13%. The vinyl polymer microparticles of Comparative Example 5 had a volume average particle size of 3.65 μm, and a proportion of vinyl polymer microparticles having a particle size of 1.7 times or more and 2.5 times or less a volume average particle size on a number basis was 0.123%, and a coefficient of variation of particle sizes was 35.3% on a volume basis. In addition, when stirring is performed at 5650 rpm for 10 minutes (at the time before classification), the volume average particle size was 3.71 μm; the proportion of vinyl polymer microparticles having a particle size of 1.7 times or more and 2.5 times or less a volume average particle size on a number basis was 0.142%; and the coefficient of variation of particle sizes was 36.2% on a volume basis.

(51) TABLE-US-00001 TABLE 1 Microparticles Particle Particle size of 1.7 size of 2.5 Number of Proportion of Number of Drop-off times a times a particles particles Particles Volume volume volume (C) having having a Total Drop-off Stirrer average average average a particle particle number number Rotation Rotation particle Coefficient particle particle size of size of of of Drop-off speed time size(D) of variation size (A) size (B) (A) − (B) (A) − (B) particles particles rate rpm min μm % μm μm number % number number % Example 1 4700 30 3.92 34.8 6.66 9.80 64 0.006 460 51 11.1 Example 2 4500 30 5.04 36.7 8.57 12.60 224 0.022 328 46 14.0 Comparative 5500 10 4.01 39.8 6.82 10.03 565 0.057 556 59 10.6 Example 1 Comparative 5000 10 4.76 37.4 8.09 11.90 424 0.042 406 50 12.3 Example 2 Comparative 5500 40 3.58 36.5 6.09 8.95 243 0.024 1161 118 10.2 Example 3 Comparative 5700 40 3.22 34.7 5.47 8.05 348 0.035 977 85 8.7 Example 4 Volume of Drop-off Particles Coefficient Characteristics Total Average of friction of Microparticles volume of volume per Coefficient Coefficient Residual Observation drop-off particles of static of kinetic amount of Hydro- number particles (V) friction friction MMA phobicity (C)/(D) (C)/(V) number μm.sup.3 μm.sup.3 — — ppm — number/μm number/μm.sup.3 Example 1 331 13009 39 0.16 0.09 36 A 16 1.6 Example 2 342 16389 48 0.17 0.09 30 A 44 4.7 Comparative 439 24154 55 0.16 0.08 27 A 141 10.3 Example 1 Comparative 580 35392 61 0.17 0.08 19 A 89 6.9 Example 2 Comparative 336 8087 24 0.17 0.10 909 B 68 10.1 Example 3 Comparative 325 5814 18 0.16 0.09 708 B 108 19.5 Example 4

(52) As is apparent from Table 1, by adjusting a proportion of vinyl polymer microparticles having a particle size of 1.7 times or more and 2.5 times or less a volume average particle size on a number basis to 0.040% or less, as well as by adjusting a volume average particle size to 3.7 μm or more, it was possible to reduce an average volume of the microparticles dropping off from a film surface while reducing film friction. In addition, appearance of the film could be improved.