Gluing and gradient low-temperature pressing process for paper-plastic package

Abstract

The invention discloses a gluing and gradient low-temperature pressing process for paper-plastic packaging, which comprises the following steps: S1, pretreating a base material: inspecting a printed paper-plastic composite base material, placing in a constant-temperature and constant-humidity environment for 20-24 hours, and balancing the moisture content to 5-7%; the base material is placed on a production line of a bag making machine, and the easy-to-tear line is formed through a magnetic knife; s3, point coating type gluing is conducted, specifically, a concave-convex tooth-shaped gluing roller is adopted, the heat sealing face of the paper-plastic composite base material is coated with the POE / PLA composite hot melt adhesive, and the gluing amount is 2.2-2.6 g / m < 2 >; and S4, pre-crosslinking treatment is conducted, specifically, UV irradiation is conducted on the glued base material, the irradiation wavelength is 254 nm, the irradiation time is 0.1-0.2 s, and the surface of the glue layer is preliminarily cured. The paper-plastic packaging gluing and pressing process which is low in gluing amount and gradient in low-temperature pressing, has an antibacterial function and is matched with a thin paper base material is adopted, and the paper-plastic packaging gluing and pressing process has the advantages of being low in glue overflowing rate, high in product percent of pass, capable of improving sanitation performance, stable in bonding performance and better in environmental protection performance.

Description

Technical Field

[0001] This invention relates to the field of paper-plastic packaging sealing and heat sealing technology for cotton soft towels, and particularly to a coating and gradient low-temperature heat sealing process for paper-plastic packaging. Background Technology

[0002] Cotton soft towel paper-plastic packaging is favored by consumers for its excellent antibacterial and dustproof properties, superior sealing, high-end texture, and safety and durability. Compared with pure plastic packaging, the paper layer of paper-plastic packaging enhances the printing quality, and the paper part is easy to degrade, making it more environmentally friendly. Compared with pure paper packaging, its plastic layer enhances its moisture protection capabilities.

[0003] The existing paper-plastic packaging materials are OPP (matte polypropylene) and coated paper. The OPP (matte polypropylene) thickness is 18-25µm, and the total thickness is 130-150µm. The coated paper is 45g paper coated (70% PE + 30% PP). The coated paper contains PE, which ensures that the packaging has a certain degree of flexibility. The coated paper contains a certain amount of PP, which is the same as the outer layer material, ensuring that the A and B sides can be heat-sealed normally. However, due to the relatively wide heat sealing width (7mm) and the uneven paper surface, the heat needs to be transferred through a heat exchanger. The OPP paper layer is transferred to the inner layer, so the heat sealing temperature is relatively high (170-205℃), which makes the paper-plastic packaging easy to be burned during the heat sealing process, affecting the appearance of the product and causing abnormal waste. In the existing technology, the paper-plastic packaging coating and heat sealing process mostly uses single EVA or polyolefin hot melt adhesive, the coating amount is usually 3-5g / ㎡, the heat sealing temperature is 90-105℃, and the process steps are mostly three-stage: "coating → heat sealing → cutting" (such as the paper-plastic composite bag heat sealing process disclosed in announcement number: CN202010109455.2).

[0004] This type of process has the following drawbacks: First, the amount of glue applied is relatively large, which can easily lead to glue overflow during the heat sealing process, contaminating the packaging surface or clogging the production equipment; second, the heat sealing temperature is too high, which can easily cause burns and carbonization problems for thin paper substrates with a basis weight of ≤60g / ㎡; third, the glue layer is mostly a single component and does not have antibacterial function, making it difficult to meet the hygiene requirements of daily chemical products; fourth, the use of flat glue rollers and rigid heat pressing molds results in uneven distribution of heat pressing pressure, which can easily lead to localized poor adhesion or paper damage. Summary of the Invention

[0005] In view of the shortcomings and defects in the existing technology, the present invention proposes a coating and gradient low temperature heat pressing process for paper-plastic packaging to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A paper-plastic packaging coating and gradient low-temperature heat pressing process includes the following steps: Step S1, Substrate Pretreatment: After inspection, the printed paper-plastic composite substrate is placed in a constant temperature and humidity environment for 20-24 hours to balance the moisture content to 5-7%; Step S2, make easy-tear lines: Place the substrate on the bag making machine production line and make easy-tear lines using a magnetic knife; Step S3, dot-coating: Using a toothed coating roller, apply POE / PLA composite hot melt adhesive to the heat-sealed surface of the paper-plastic composite substrate, with an adhesive application amount of 2.2-2.6 g / ㎡; Step S4, pre-crosslinking treatment: The substrate after coating is subjected to UV irradiation with a wavelength of 254nm and an irradiation time of 0.1-0.2s to allow the surface of the adhesive layer to be initially cured. Step S5, Gradient Low-Temperature Pressing: Two-stage hot pressing blades are used, with belt rollers running, to perform two stages of pressing in sequence. The first stage pressing temperature is 78-82℃, the pressure is 0.12-0.15MPa, and the time is 0.1-0.2s; the second stage pressing temperature is 83-88℃, the pressure is 0.15-0.18MPa, and the time is 0.1-0.2s. Step S6, online cooling and shaping: The pressed substrate is sent into the cooling channel, the cooling temperature is 20-25℃, and the cooling time is 0.3-0.5s; Step S7, Cutting and Shaping: Cut according to the packaging specifications to obtain the finished paper-plastic packaging.

[0007] Preferably, the humidity of the constant temperature and humidity environment in step S1 is 45-55%, and the temperature is 20-25℃.

[0008] Preferably, the POE / PLA composite hot melt adhesive in step S3 is composed of the following components in parts by weight: 65-70 parts POE, 25-30 parts PLA, 6-8 parts nano silica antibacterial agent, and 1-2 parts antioxidant.

[0009] Preferably, the surface of the toothed coating roller in step S3 is provided with diamond-shaped protrusions, the tooth pitch is 2mm, and the tooth height is 0.5mm.

[0010] Preferably, the UV irradiation intensity in step S4 is 80-100 mW / cm².

[0011] Preferably, the composite substrate is OPP (18-25µm) + textured paper (40-60g) + coating (PE 60-70% + PP 40-30%) (25-30µm).

[0012] Compared with the prior art, the beneficial effects of this invention are as follows: (1) Low glue overflow rate: By combining spot coating with pre-crosslinking treatment, the amount of glue applied is small and the glue overflow rate is less than 1%. (2) Improved product qualification rate: The heat sealing temperature is as low as 78-88℃, and the heat sealing breakage rate of paper-plastic bags is 0; (3) Improved hygiene performance: The nano-silica antibacterial agent in the composite adhesive layer has a kill rate of ≥99% against Escherichia coli and Staphylococcus aureus, meeting the hygiene requirements for daily chemical product packaging; (4) Stable bonding performance: The combination of adhesive application and gradient pressing results in a bonding strength ≥40N / 15mm, and the bonding strength retention rate is ≥90% after storage at low temperature (-18℃) and high temperature (50℃); (5) Better environmental performance: The composite adhesive layer is biodegradable and can be naturally degraded, which is in line with the industry development trend of "reducing plastic and waste". Detailed Implementation

[0013] In the description of this invention, the described embodiments are only some embodiments of this invention, and not all embodiments. Example

[0014] A paper-plastic packaging coating and gradient low-temperature heat pressing process includes the following steps: Step S1, Substrate Pretreatment: After inspection, the printed paper-plastic composite substrate is placed in a constant temperature and humidity environment for 20 hours to balance the moisture content to 5%; Step S2, make easy-tear lines: Place the substrate on the bag making machine production line and make easy-tear lines using a magnetic knife; Step S3, dot-coating: Using a toothed coating roller, apply POE / PLA composite hot melt adhesive to the heat-sealed surface of the paper-plastic composite substrate, with a coating amount of 2.2 g / ㎡; Step S4, pre-crosslinking treatment: The substrate after coating is subjected to UV irradiation with a wavelength of 254nm and an irradiation time of 0.1s to allow the surface of the adhesive layer to be initially cured. Step S5, Gradient low-temperature pressing: Two-stage hot pressing blades are used, with belt rollers running, to perform two stages of pressing in sequence. The first stage pressing temperature is 78℃, the pressure is 0.12MPa, and the time is 0.1s; the second stage pressing temperature is 83℃, the pressure is 0.15MPa, and the time is 0.1s. Step S6, online cooling and shaping: The hot-pressed substrate is sent into the cooling channel, the cooling temperature is 20℃, and the cooling time is 0.3s; Step S7, Cutting and Shaping: Cut according to the packaging specifications to obtain the finished paper-plastic packaging.

[0015] The constant temperature and humidity environment in step S1 has a humidity of 45% and a temperature of 20°C.

[0016] In step S3, the POE / PLA composite hot melt adhesive is composed of the following components in parts by weight: 65 parts POE, 25 parts PLA, 6 parts nano silica antibacterial agent, and 1 part antioxidant.

[0017] The surface of the toothed coating roller in step S3 is provided with diamond-shaped protrusions, the tooth pitch is 2mm and the tooth height is 0.5mm.

[0018] The UV irradiation intensity in step S4 is 80 mW / cm².

[0019] The composite substrate is OPP (18-25µm) + textured paper (40-60g) + coating (PE 60-70% + PP 40-30%) (25-30µm). Example

[0020] A paper-plastic packaging coating and gradient low-temperature heat pressing process includes the following steps: Step S1, Substrate Pretreatment: After inspection, the printed paper-plastic composite substrate is placed in a constant temperature and humidity environment for 21 hours to balance the moisture content to 5%; Step S2, make easy-tear lines: Place the substrate on the bag making machine production line and make easy-tear lines using a magnetic knife; Step S3, dot-coating: Using a toothed coating roller, apply POE / PLA composite hot melt adhesive to the heat-sealed surface of the paper-plastic composite substrate, with a coating amount of 2.3 g / ㎡; Step S4, pre-crosslinking treatment: The substrate after coating is subjected to UV irradiation with a wavelength of 254nm and an irradiation time of 0.1s to allow the surface of the adhesive layer to be initially cured. Step S5, Gradient low-temperature pressing: Two-stage hot pressing blades are used, with belt rollers running, to perform two stages of pressing in sequence. The first stage pressing temperature is 80℃, the pressure is 0.13MPa, and the time is 0.1s; the second stage pressing temperature is 84℃, the pressure is 0.16MPa, and the time is 0.1s. Step S6, online cooling and shaping: The hot-pressed substrate is sent into the cooling channel, the cooling temperature is 22℃, and the cooling time is 0.4s; Step S7, Cutting and Shaping: Cut according to the packaging specifications to obtain the finished paper-plastic packaging.

[0021] The constant temperature and humidity environment in step S1 has a humidity of 50% and a temperature of 22°C.

[0022] In step S3, the POE / PLA composite hot melt adhesive is composed of the following components in parts by weight: 66 parts POE, 26 parts PLA, 6 parts nano silica antibacterial agent, and 1 part antioxidant.

[0023] The surface of the toothed coating roller in step S3 is provided with diamond-shaped protrusions, the tooth pitch is 2mm and the tooth height is 0.5mm.

[0024] The UV irradiation intensity in step S4 is 85 mW / cm².

[0025] The composite substrate is OPP (18-25µm) + textured paper (40-60g) + coating (PE 60-70% + PP 40-30%) (25-30µm). Example

[0026] A paper-plastic packaging coating and gradient low-temperature heat pressing process includes the following steps: Step S1, Substrate Pretreatment: After inspection, the printed paper-plastic composite substrate is placed in a constant temperature and humidity environment for 22 hours to balance the moisture content to 6%; Step S2, make easy-tear lines: Place the substrate on the bag making machine production line and make easy-tear lines using a magnetic knife; Step S3, dot-coating: Using a toothed coating roller, apply POE / PLA composite hot melt adhesive to the heat-sealing surface of the paper-plastic composite substrate, with a coating amount of 2.4 g / ㎡; Step S4, pre-crosslinking treatment: The substrate after coating is subjected to UV irradiation with a wavelength of 254nm and an irradiation time of 0.15s to allow the surface of the adhesive layer to be initially cured. Step S5, Gradient low-temperature pressing: Two-stage hot pressing blades are used, with belt rollers running, to perform two stages of pressing in sequence. The first stage pressing temperature is 80℃, the pressure is 0.13MPa, and the time is 0.15s; the second stage pressing temperature is 85℃, the pressure is 0.16MPa, and the time is 0.15s. Step S6, online cooling and shaping: The hot-pressed substrate is sent into the cooling channel, the cooling temperature is 23℃, and the cooling time is 0.4s; Step S7, Cutting and Shaping: Cut according to the packaging specifications to obtain the finished paper-plastic packaging.

[0027] The constant temperature and humidity environment in step S1 has a humidity of 50% and a temperature of 23°C.

[0028] In step S3, the POE / PLA composite hot melt adhesive is composed of the following components in parts by weight: 68 parts POE, 28 parts PLA, 7 parts nano silica antibacterial agent, and 1.5 parts antioxidant.

[0029] The surface of the toothed coating roller in step S3 is provided with diamond-shaped protrusions, the tooth pitch is 2mm and the tooth height is 0.5mm.

[0030] The UV irradiation intensity in step S4 is 90 mW / cm².

[0031] The composite substrate is OPP (18-25µm) + textured paper (40-60g) + coating (PE 60-70% + PP 40-30%) (25-30µm). Example

[0032] A paper-plastic packaging coating and gradient low-temperature heat pressing process includes the following steps: Step S1, Substrate Pretreatment: After inspection, the printed paper-plastic composite substrate is placed in a constant temperature and humidity environment for 23 hours to balance the moisture content to 6%; Step S2, make easy-tear lines: Place the substrate on the bag making machine production line and make easy-tear lines using a magnetic knife; Step S3, dot-coating: Using a toothed coating roller, apply POE / PLA composite hot melt adhesive to the heat-sealed surface of the paper-plastic composite substrate, with a coating amount of 2.5g / ㎡; Step S4, pre-crosslinking treatment: The substrate after coating is subjected to UV irradiation with a wavelength of 254nm and an irradiation time of 0.2s to allow the surface of the adhesive layer to be initially cured. Step S5, Gradient low-temperature pressing: Two-stage hot pressing blades are used, with belt rollers running, to perform two stages of pressing in sequence. The first stage pressing temperature is 81℃, the pressure is 0.14MPa, and the time is 0.2s; the second stage pressing temperature is 86℃, the pressure is 0.17MPa, and the time is 0.2s. Step S6, online cooling and shaping: The hot-pressed substrate is sent into the cooling channel, the cooling temperature is 23℃, and the cooling time is 0.4s; Step S7, Cutting and Shaping: Cut according to the packaging specifications to obtain the finished paper-plastic packaging.

[0033] The constant temperature and humidity environment in step S1 has a humidity of 50% and a temperature of 24℃.

[0034] In step S3, the POE / PLA composite hot melt adhesive is composed of the following components in parts by weight: 69 parts POE, 29 parts PLA, 8 parts nano silica antibacterial agent, and 2 parts antioxidant.

[0035] The surface of the toothed coating roller in step S3 is provided with diamond-shaped protrusions, the tooth pitch is 2mm and the tooth height is 0.5mm.

[0036] The UV irradiation intensity in step S4 is 95 mW / cm².

[0037] The composite substrate is OPP (18-25µm) + textured paper (40-60g) + coating (PE 60-70% + PP 40-30%) (25-30µm). Example

[0038] A paper-plastic packaging coating and gradient low-temperature heat pressing process includes the following steps: Step S1, Substrate Pretreatment: After inspection, the printed paper-plastic composite substrate is placed in a constant temperature and humidity environment for 24 hours to balance the moisture content to 7%; Step S2, make easy-tear lines: Place the substrate on the bag making machine production line and make easy-tear lines using a magnetic knife; Step S3, dot-coating: Using a toothed coating roller, apply POE / PLA composite hot melt adhesive to the heat-sealing surface of the paper-plastic composite substrate, with a coating amount of 2.6 g / ㎡; Step S4, pre-crosslinking treatment: The substrate after coating is subjected to UV irradiation with a wavelength of 254nm and an irradiation time of 0.2s to allow the surface of the adhesive layer to be initially cured. Step S5, Gradient low-temperature pressing: Two-stage hot pressing blades are used, with belt rollers running, to perform two stages of pressing in sequence. The first stage pressing temperature is 82℃, the pressure is 0.15MPa, and the time is 0.2s; the second stage pressing temperature is 88℃, the pressure is 0.18MPa, and the time is 0.2s. Step S6, online cooling and shaping: The hot-pressed substrate is sent into the cooling channel, the cooling temperature is 25℃, and the cooling time is 0.5s; Step S7, Cutting and Shaping: Cut according to the packaging specifications to obtain the finished paper-plastic packaging.

[0039] The constant temperature and humidity environment in step S1 has a humidity of 55% and a temperature of 25°C.

[0040] In step S3, the POE / PLA composite hot melt adhesive is composed of the following components in parts by weight: 70 parts POE, 30 parts PLA, 8 parts nano silica antibacterial agent, and 2 parts antioxidant.

[0041] The surface of the toothed coating roller in step S3 is provided with diamond-shaped protrusions, the tooth pitch is 2mm and the tooth height is 0.5mm.

[0042] The UV irradiation intensity in step S4 is 100 mW / cm².

[0043] The composite substrate is OPP (18-25µm) + textured paper (40-60g) + coating (PE 60-70% + PP 40-30%) (25-30µm).

[0044] In use, this invention combines dot-applied adhesive with pre-crosslinking treatment, resulting in a smaller amount of adhesive applied and an overflow rate of less than 1%, significantly reducing the overflow rate. The heat sealing temperature is as low as 78-88℃, ensuring a zero heat-sealing breakage rate for paper-plastic bags and greatly improving product qualification rate. The nano-silica antibacterial agent in the composite adhesive layer has a kill rate of ≥99% against Escherichia coli and Staphylococcus aureus, meeting the hygiene requirements for daily chemical product packaging and effectively improving hygiene performance. The combination of adhesive application and gradient heat sealing results in a bonding strength of ≥40N / 15mm, and the bonding strength retention rate after storage at low temperatures (-18℃) and high temperatures (50℃) is ≥90%, making the bonding performance more stable. The use of PLA biodegradable components allows the composite adhesive layer to degrade naturally, conforming to the industry trend of "reducing plastic and waste" and making it more environmentally friendly.

[0045] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A coating and gradient low-temperature hot stamping process for paper-plastic packaging, characterized in that, Includes the following steps: Step S1, Substrate Pretreatment: After inspection, the printed paper-plastic composite substrate is placed in a constant temperature and humidity environment for 20-24 hours to balance the moisture content to 5-7%; Step S2, make easy-tear lines: Place the substrate on the bag making machine production line and make easy-tear lines using a magnetic knife; Step S3, dot-coating: Using a toothed coating roller, apply POE / PLA composite hot melt adhesive to the heat-sealed surface of the paper-plastic composite substrate, with an adhesive application amount of 2.2-2.6 g / ㎡; Step S4, pre-crosslinking treatment: The substrate after coating is subjected to UV irradiation with a wavelength of 254nm and an irradiation time of 0.1-0.2s to allow the surface of the adhesive layer to be initially cured. Step S5, Gradient Low-Temperature Pressing: Two-stage hot pressing blades are used, with belt rollers running, to perform two stages of pressing in sequence. The first stage pressing temperature is 78-82℃, the pressure is 0.12-0.15MPa, and the time is 0.1-0.2s; the second stage pressing temperature is 83-88℃, the pressure is 0.15-0.18MPa, and the time is 0.1-0.2s. Step S6, online cooling and shaping: The pressed substrate is sent into the cooling channel, the cooling temperature is 20-25℃, and the cooling time is 0.3-0.5s; Step S7, Cutting and Shaping: Cut according to the packaging specifications to obtain the finished paper-plastic packaging.

2. The coating and gradient low-temperature heat pressing process for paper-plastic packaging according to claim 1, characterized in that, The constant temperature and humidity environment in step S1 has a humidity of 45-55% and a temperature of 20-25℃.

3. The coating and gradient low-temperature heat pressing process for paper-plastic packaging according to claim 1, characterized in that, In step S3, the POE / PLA composite hot melt adhesive is composed of the following components in parts by weight: 65-70 parts POE, 25-30 parts PLA, 6-8 parts nano silica antibacterial agent, and 1-2 parts antioxidant.

4. The coating and gradient low-temperature heat pressing process for paper-plastic packaging according to claim 1, characterized in that, The surface of the toothed coating roller in step S3 is provided with diamond-shaped protrusions, the tooth pitch is 2mm and the tooth height is 0.5mm.

5. The coating and gradient low-temperature heat pressing process for paper-plastic packaging according to claim 1, characterized in that, The UV irradiation intensity in step S4 is 80-100 mW / cm².

6. The coating and gradient low-temperature heat pressing process for paper-plastic packaging according to claim 1, characterized in that, The composite substrate is OPP (18-25µm) + textured paper (40-60g) + coating (PE 60-70% + PP 40-30%) (25-30µm).