做薄膜的圈子里有条心照不宣的鄙视链：做高端包装膜的，看不起做农膜的；做农膜的，又看不起拿副牌料凑数的。可每年开春一铺地膜、一上大棚，翻车翻得凶的，恰恰是那张被人嫌弃的便宜膜。
山东青岛那边一家做棚膜的，去年开春图便宜换了一批杂牌再生料，铺下去俩月就粉化成渣，一亩地赔小两千，一棚菜全完。老板蹲在地头抽烟想不通：同样是LDPE，凭啥有人用着没事，他用着就出事？
说白了，不是LDPE不行，是他没把“原厂副牌”和“回料再生”这两码事分开。这篇就把LDPE这门高压老手艺、三家国外头部大厂、还有副牌料的门道，一次讲透。
高压釜里炸出来的薄膜老炮
LDPE，低密度聚乙烯，跟HDPE、LLDPE是一家三兄弟，但脾气完全不同。它是在1500到3000个大气压的高压釜或管式反应器里“炸”出来的，分子链上挂着一堆长短不一的支链，结晶度低，所以软、透明、热封性好、低温不断。
说白了，HDPE是直杆，LLDPE是带短枝的杆，LDPE是一棵枝杈乱长的小树。正是这些乱枝杈，让它吹出来的膜又柔又韧，热封温度还低。全球LDPE产能里，薄膜和挤出涂层占了大头，农膜、重包装袋、复合膜热封层都离不开它。
副牌不是回料，是同一批长支链聚合物
讲副牌之前，先把概念掰碎。副牌，是同一厂家、同一牌号里，出厂检验没完全达到正牌技术指标的那一部分。它的来源就四类：装置开停车时的头尾不稳定料；牌号切换时的过渡料；工艺波动导致熔指、色相、透光某项小幅超标的批次；还有副线的尾料。
关键在这——它还是原厂原生聚合粒子，分子结构和正牌一模一样，只是个别指标小幅浮动，不是废旧塑料再造粒。把边界画清楚：
| 类型 | 来源 | 品质 | 典型用途 |
|---|
| 正牌 | 原厂达标批次 | 全指标达标、批次稳 | 高要求膜、认证件 |
| 副牌 | 原厂未达标批次 | 个别指标小幅偏离，基材一致 | 内袋、配色膜、一般农膜 |
| 回料/水口料 | 加工边角料再造粒 | 已受过一次热历史 | 低要求制品 |
| 再生料 | 废旧塑料回收造粒 | 性能波动大 | 低端填充 |
LDPE副牌能在薄膜上落地，靠的就是它差的那一项，往往是透光或色相，吹膜性能基本不动。做棚膜、做内袋，透光差一点根本没人计较。
埃克森美孚：高压釜技术的活化石
全球LDPE产能靠前的国外厂，头部梯队绕不开三家：埃克森美孚、陶氏、利安德巴塞尔，SABIC紧随其后。
埃克森美孚是其中产能规模靠前的一家，全球LDPE年产能估计在480万吨上下，比利时梅尔豪特那套装置单线年产能50万吨，是全球产能靠前的单线LDPE生产线。它家代表牌号是ExxonMobil™ LDPE LD 150系列，比如LD 150BW，薄膜级，吹膜挺度好，适合收缩膜、冷冻膜和农膜。
它家副牌的特点是：高压法老装置跑了几十年，批次数据全，副牌主要落在熔指和添加剂微调上，做通用膜和农膜兜底很稳。
陶氏：把薄膜光学性写进教科书的那家
陶氏在LDPE上的全球份额大约在9%到12%这一档，代表牌号是Dow™ LDPE系列，150E、310E、780E、722，还有Agility™ EC7000涂层级。陶氏的强项在薄膜光学性能和挤出涂层，做重包装膜、挂面纸涂层的客户认它。
陶氏副牌料的特点是：指标偏离多落在熔指细微波动上，吹膜、涂层工序窗口宽，内行人常拿来做复合膜的芯层和热封层，性能够、成本低。
利安德巴塞尔：高压法产品线铺得宽的那家
利安德巴塞尔在全球LDPE份额约11%上下，旗下两个牌子：Lupolen®，比如2410T注塑级、2012D电缆级；还有Petrothene L3035收缩膜级。它家装置横跨欧美亚，牌号铺得广，从薄膜到注塑到电缆都有。
它家副牌的好处是来源杂、规格全，做配色膜、做通用内衬袋时，挑得到接近自己工艺的牌号，不用硬改工艺参数。
选副牌，先认厂再测熔指
说几个实操坑。先说颜色。LDPE副牌常见的偏差项是透光、色相、熔指，吹膜前先测熔指，熔指差太多，膜厚均匀性直接乱。再就是认准原厂原包。副牌也有大包装和小包装，大包装吨袋适合大厂连续跑线，小包装适合小线试机。还有留样可溯。每批进厂留样，吹膜试样留底，出问题能倒查到批次。
末了是用途匹配。高透明食品膜别用副牌，棚膜、内衬袋、重包装内袋用副牌，刚好把出厂检验多扣的那部分指标吃掉。
科隆仓库现货｜LDPE稳定
主推品牌：埃克森美孚、陶氏、利安德巴塞尔
主要牌号：ExxonMobil LD150系列、Dow LDPE、Lupolen/Petrothene
包装规格：大包装、小包装均有现货
仓库现货通常在3000-6000吨：小包副牌备货500-800吨、箱装副牌备货200-400吨、大包料/吨包料备货2500-4800吨
供应保障：原厂原包直采
青岛棚膜：一柜副牌省出半季肥料钱
说个实际案例。山东青岛有家做大棚农膜的客户，之前一直用国产再生料掺配，透光率年年波动，棚里草莓苗期发黄，农户投诉不断。后来换成进口大厂LDPE副牌料，熔指和基材稳定性拉齐，透光率波动从8%压到2%以内，开春返工率降了七成。
材料一吨下来省了一千多，一年少赔的农户纠纷，够买半棚新膜。这就是选料的账——不是挑便宜，是挑“基材和正牌一条心”的原厂副牌。宁波市科隆新材料有限公司常年做进口大厂副牌料，类似的薄膜、农膜选型案子每年处理不少，说白了就是帮你把“吹得稳、不闹事”这件事，在开机之前定下来。
八条口诀，LDPE副牌不翻车
1. 高透明食品膜——用正牌，别碰副牌；
2. 棚膜、地膜、内衬袋——副牌能兜底；
3. 熔指先测再上机，差太多直接退；
4. 认准原厂原包，大包装跑量、小包装试机；
5. 透光色相偏差，做内袋无所谓；
6. 复合膜热封层、芯层——副牌主战场；
7. 每批留样，出问题能倒查；
8. 价格低得离谱的，多半是再生料冒充。
收尾几句
LDPE这东西，是高压釜里“炸”出来的老手艺，软、透明、热封好，薄膜和农膜离不开它。副牌料不是次品，是高压自由基聚合线上同一批长支链聚合物——分子链没换，只是熔指和透光在出厂检验时多扣了两分。选对厂、测准熔指、用对场景，它就是你成本表上那块稳稳的压舱石。
In the film industry, there's an unspoken hierarchy of disdain: those making high-end packaging films look down on those who make agricultural films; those who make agricultural films look down on those who use off-label materials to fill the numbers. But every spring, when you lay plastic mulch and set up greenhouses, the ones that fail badly are precisely that cheap film that people dislike.
A greenhouse film maker in Qingdao, Shandong, last spring bought a batch of off-label recycled materials cheaply, and after two months of laying, they crumbled to dust, losing nearly 2,000 yuan per mu, and the whole greenhouse was finished. The boss squatted at the edge of the field smoking, puzzled: it's LDPE, so why is it that some people have no problems using it, while others have problems?
To put it bluntly, it's not that LDPE is ineffective, but that they haven't separated the two things of "original sub-brand" and "recycled material." This article will thoroughly explain the old high-pressure process of LDPE, three leading foreign manufacturers, and the sub-brand material at once.
The
LDPE old film blasted in the autoclave is low-density polyethylene, which is like three brothers to HDPE and LLDPE but has a completely different temperament. It is "blown out" in an autoclave or tubular reactor at 1500 to 3000 atmospheres, with a cluster of branches of varying lengths hanging on the molecular chains, resulting in low crystallinity, making it soft, transparent, heat-sealable, and continuously low-temperature conditions.
To put it simply, HDPE is a straight rod, LLDPE is a rod with short branches, and LDPE is a small tree with tangled branches. It is precisely these tangled branches that make the film it produces soft and tough, with a low heat sealing temperature. In global LDPE production capacity, film and extrusion coatings make up the majority; agricultural films, heavy packaging bags, and composite film heat sealing all rely on them.
Sub-brand is not recycled material, but a batch of long-chain polymers
Before talking about sub-brands, let's break down the concept. Sub-brands are the parts of the same manufacturer and grade that have not fully met the official technical specifications during factory inspection. Their sources fall into four categories: unstable materials from the end of the unit when starting and shutting down; transition materials when switching grades; Process fluctuations caused some batches to slightly exceed standards in melt index, hue, and light transmission; And leftover material from the secondary line.
The key is here—it's still original original polymerized particles, with molecular structure identical to the genuine brand, only minor fluctuations in some indicators, not recycled waste plastic pellets. Clearly draw boundaries:
| Type | Source | Quality | Typical Use |
|---|
| Genuine Brand | Original Factory Standard Batch | Full Indicator Compliant, Batch Stable | High-Requirement Film, Certified Parts |
| Subbrand | Original factory non-compliant batch | Slight deviations in some indicators, substrate consistency | Inner bag, color-matching film, general agricultural film |
| Reused/sprue material | Processed scraps repelled and pelletized | Already experienced once in heat history | Low requirements products |
| Regenerated material | Recycled Plastic Pelletizing | Significant Performance Fluctuations | Low-End Filler |
LDPE The reason sub-brands can land on film is because of its weak aspects, often light transmission or hue, with basically unchanged film blowing performance. For greenhouse films and inner bags, no one really cares about poor light transmission.
ExxonMobil: The living fossil of autoclave technology
The top foreign factories in global LDPE capacity have three leading companies: ExxonMobil, Dow, and Leanderbaster, with SABIC following closely behind.
ExxonMobil is one of the largest in terms of capacity, with global annual LDPE capacity estimated at around 4.8 million tons. Belgium's Meerhout unit has a single-line annual capacity of 500,000 tons, making it one of the world's leading single-line LDPE production lines. Their representative grade is the ExxonMobil™ LDPE LD 150 series, such as LD 150BW, film grade, good blown film stiffness, suitable for shrink film, cryofilm, and agricultural film.
Their secondary brand features decades of running high-pressure Pharaoh units, complete batch data, mainly focusing on melting fingers and additive fine-tuning, providing reliable support for general-purpose and agricultural films.
Dow: The company that wrote film optics in textbooks
Dow's global share in LDPE is about 9% to 12%, with Dow™ LDPE series as representative grades: 150E, 310E, 780E, 722, and Agility™ EC7000 coating grade. Dow's strengths lie in the optical performance of thin films and extrusion coatings, recognized by customers specializing in heavy packaging films and hanging paper coatings. The characteristics of
Dow's secondary brand materials are: indicators mostly deviate due to slight fluctuations in the melting index, with wide window for blown film and coating processes. Insiders often use them for core and heat seal layers of composite films, offering high performance and low cost.
Leanderbasel: The company with a broad high-pressure product line
Leanderbasel, with about 11% global LDPE market share, owning two brands: Lupolen®, such as 2410T injection molding grade and 2012D cable grade; and Petrothene L3035 shrink film grade. Their equipment spans Europe, America, and Asia, with a wide range of grades, covering everything from film to injection molding to cables. The advantage of
's sub-brand is that it comes from a wide range of sources and specifications. When making color films or general lining bags, you can pick a grade close to your own process without having to force changes to process parameters.
When choosing a sub-brand, first identify the factory and then test the melt index .
will share a few practical pitfalls. Let's talk about color first. Common deviations with LDPE sub-brands are light transmission, hue, and melt index. Before blowing the film, the melt index is tested; if the melt index differs too much, the film thickness uniformity will be disrupted. Also, make sure to make the original factory packaging. Sub-brands also have large and small packages. Large packaging per ton bag is suitable for continuous production lines at big factories, small packaging is suitable for small line testing. There are also traceable samples. Samples are kept at the factory after each batch arrives, and the film blowing samples are kept as a backup. If problems arise, you can trace back to the batch.
Finally, use matching. Do not use secondary labels for high-transparency food films; use secondary labels for greenhouse film, lining bags, and heavy packaging inner bags, as this will just absorb the excess quota from factory inspection.
Cologne warehouse in stock | LDPE stable
Main brands: ExxonMobil, Dow, Liander Basel
Main grades: ExxonMobil LD150 series, Dow LDPE, Lupolen/Petrothene
Packaging specifications: both large and small packages are in stock
warehouse stock is usually between 3000-6000 tons: small sub-brand stock 500-800 tons, sub-brand containerized stock 200-400 tons, large package/ton package material stock 2500-4800 tons
supply guarantee: direct procurement from original factory and package
Qingdao greenhouse film: one sub-label container saves half a season's fertilizer cost
a real case. In Qingdao, Shandong, a client who made greenhouse agricultural film had previously used domestically produced recycled materials for blending, causing the light transmittance to fluctuate every year. The strawberries in the greenhouses turned yellow during the seedling stage, and farmers kept complaining. Later, they switched to LDPE sub-brand material from a major imported manufacturer, with melting fingers and substrate stabilizing evenly, reducing light transmittance fluctuation from 8% to below 2%, and the rework rate dropped by 70% in spring.
saved over a thousand yuan per ton of material, enough to buy half a new greenhouse film for farmers who lost compensation in a year. This is the account of material selection—not choosing cheap, but choosing the original sub-brand brand that "bases and genuine brands are united." Ningbo Kelong New Materials Co., Ltd. has long been handling imported major manufacturers' sub-brand materials. They handle many similar film and agricultural film selection cases every year. Simply put, they help you decide on the principle of "blowing steadily without causing trouble" before starting the machine.
Eight tips to avoid LDPE sub-brand failures
1. High-transparency food film—use genuine brand, don't touch sub-brand;
2. Greenhouse film, mulch film, lining bag—sub-brand can provide a backup;
3. Test the melting finger before machine use; if too much is off, return it immediately;
4. Make sure to choose original factory packaging: use large packages for bulk production, small packages for trial runs;
5. Slight deviations in transparency or color are fine for inner bags;
6. Composite film heat-seal layer and core layer — main battlefield for secondary brands;
7. Keep samples from each batch so problems can be traced back;
8. Prices that are ridiculously low are mostly recycled materials pretending to be new.
Closing Words
LDPE is a thing that comes from the traditional method of being 'cooked' in a high-pressure autoclave. It is soft, transparent, seals well with heat, and is indispensable for films and agricultural films. Secondary brand material is not inferior; it is the same batch of long-chain polymers produced on the high-pressure free radical polymerization line — the molecular chains haven't changed, only the melt index and transparency are deducted a couple of points in factory inspection. Choosing the right manufacturer, measuring the melt index accurately, and using it in the appropriate scenario, it becomes the reliable ballast in your cost sheet.
